Wednesday, December 6, 2017

CSS Tables

Saturday, September 16, 2017

Tổng quan về Layout

Có 4 cách để layout

sd Table => cấm
sd các CSS Framework (bootstrap...)
sd CSS Float (sd pp này thì chú ý rằng thuộc tính width không phải lúc nào cũng nhìn thấy bằng cách đổi màu nền cho element)
sd CSS3 Flexbox => sẽ hiển thị sai nếu sd trình duyệt cũ

Tham khảo
https://www.w3schools.com/html/html_layout.asp

Vấn đề hay gặp khi layout website bằng css float

background-color: sẽ bôi màu lên cả content + padding
border: sẽ bôi màu ra bên ngoài padding
width: chỉ bao gồm độ rộng của content(tức là KHÔNG bao gồm padding)

vì vậy công thức để tính khoảng rộng của 1 element là:

width+2*padding+2*border+2*margin

Nhận xét:

không bao giờ có thể nhìn tường minh được phần width của một element.
chỉ có thể nhìn tường minh được phần width và padding của element (sd thuộc tính background-color)

Tham khảo:
https://www.w3schools.com/css/css_boxmodel.asp

Source code:


<!DOCTYPE html>
<html>
<head>
<style>
div {
    width: 330px;
    padding: 10px;
    margin: 0;
    background-color:gray;
}
</style>
</head>
<body>

<h2>Calculate the total width:</h2>

<img src="klematis4_big.jpg" width="350" height="263" alt="Klematis">
<div>The picture above is 350px wide. The total width of this element is also 350px.</div>

</body>
</html>

Calculate the total width:

The picture above is 350px wide. The total width of this element is also 350px.

Friday, September 15, 2017

css overflow

overflow nghĩa là "tràn ra"
diễn nôm: thuộc tính overflow dùng để mô tả cách hiển thị khi dữ liệu bị "tràn ra ngoài" cái khu vực cho phép được hiển thị của nó
--------------
div {
overflow: auto;}
ví dụ:

You can use the overflow property when you want to have better control of the layout. The overflow property specifies what happens if content overflows an element's box.

Position:sticky

Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.
Some text to enable scrolling.. Lorem ipsum dolor sit amet, illum definitiones no quo, maluisset concludaturque et eum, altera fabulas ut quo. Atqui causae gloriatur ius te, id agam omnis evertitur eum. Affert laboramus repudiandae nec et. Inciderint efficiantur his ad. Eum no molestiae voluptatibus.

I am sticky!

CSS Layout - The position Property

sử dụng để thiết lập vị trí của element
thuộc tính position có 5 gía trị, thể hiện kiểu loại vị trí

static
relative
fixed
absolute
sticky

sau đó phải thiết lập vị trí cụ thể sd 4 thuộc tính top left right bottom
top: => liên quan đến khoảng cách từ top đến vị trí của element
left: => liên quan đến khoảng cách từ left đến vị trí của element
right: => liên quan đến khoảng cách từ right đến vị trí của element
bottom: => liên quan đến khoảng cách từ bottom đến vị trí của element

position: static;

là mặc định của các element (có nghĩa là vị trí của nó là vị trí tự nhiên trong html code)
vì thế mà nếu set position:static thì 4 thuộc tính top left right bottom sẽ không có tác dụng gì cả

position: relative;

vị trí element được xác định so với vị trí mặc định của chính element đó
khi đó: giả sử khoảng cách default từ element đến top,left,right,bottom của webpage là T, L, R, B
top:X => khoảng cách từ element đến top là T+X (tăng thêm 1 lượng X nếu X>0, giảm 1 lượng X nếu X<0)


<!DOCTYPE html>
<html>
<head>
<style>
div.relative {
    position: relative;
    left: -30px;
    border: 3px solid #73AD21;
}
</style>
</head>
<body>

<h2>position: relative;</h2>

<p>An element with position: relative; is positioned relative to its normal position:</p>

<div class="relative">
This div element has position: relative;
</div>

</body>
</html>

position: fixed;

vị trí của element được xác định so với viewport(cửa sổ trình duyệt)
=> vị trí element không thay đổi khi ta scroll
top:X => khoảng cách từ element đến top của viewport(gần thanh html url của trình duyệt) là X


<!DOCTYPE html>
<html>
<head>
<style>
div.fixed {
    position: fixed;
    left: 50%;
    top: -6px;
    width: 300px;
    border: 3px solid #73AD21;
}
body{
    width:3000px;
    height:5000px;
}
</style>
</head>
<body>

<h2>position: fixed;</h2>

<p>An element with position: fixed; is positioned relative to the viewport, which means it always stays in the same place even if the page is scrolled:</p>

<div class="fixed">
This div element has position: fixed;
</div>

</body>
</html>

position: absolute;

vị trí của element được xác định so với "tổ tiên gần nhât" mà là "positioned element"
positioned element: là các element mà thuộc tính position không phải là static (tức là position thuộc 1 trong 4 giá trị relative fixed absolute và sticky)
=> nếu tất cả các element tổ tiên của nó đều là static position(position mặc định) thì :
vị trí của element được xác định so với webpage (vị trí element sẽ thay đổi khi ta scroll)


<!DOCTYPE html>
<html>
<head>
<style>
div.relative {
    position: relative;
    width: 400px;
    height: 200px;
    border: 3px solid #73AD21;
} 

div.absolute {
    position: absolute;
    top: 80px;
    right: 0;
    width: 200px;
    height: 100px;
    border: 3px solid #73AD21;
}
</style>
</head>
<body>

<h2>position: absolute;</h2>

<p>An element with position: absolute; is positioned relative to the nearest positioned ancestor (instead of positioned relative to the viewport, like fixed):</p>

<div class="relative">This div element has position: relative;
  <div class="absolute">This div element has position: absolute;</div>
</div>

</body>
</html>

position: sticky;

vị trí của element loại sticky có 2 trạng thái: relative and fixed
1. relative: vị trí element được xác định so với vị trí mặc định của chính element đó
2. fixed: vị trí của element được xác định so với viewport(cửa sổ trình duyệt)

điều kiện chuyển từ trạng thái relative sang fixed: khi vị trí của element so với viewport chạm đến 1 trong 4 thuộc tính top, left, right, bottom
Ví du: positionsticky


<!DOCTYPE html>
<html>
<head>
<style>
div.sticky {
  position: -webkit-sticky;/*For Safari*/
  position: sticky;
  top: 0;
  left:50px;
  bottom:0;
  right:0;
  padding: 5px;
  width:100px;
  background-color: #cae8ca;
  border: 2px solid #4CAF50;
}
#div1{
width:3000px;
height:5000px;
background-color:blue;
}
#div2{
width:3000px;
height:5000px;
background-color:green;
}
</style>
</head>
<body>

<div id="div1"></div>
<div class="sticky">I am sticky!</div>
<div id="div2"></div>


</body>
</html>

css layout với max-width và margin:auto

một block element sẽ có chiều rộng trải dài đến hết mức có thể
để setup chiều rộng của 1 block element
1. sử dụng width
nhược điểm: khi width của cửa sổ (viewport) nhỏ hơn độ width của element => browser sẽ add thêm horizontal scrollbar (thanh cuộn ngang)
2. sử dụng max-width
khi width của cửa sổ nhỏ hơn max-width của element
=> chiều rộng của element sẽ tự động nhỏ đi
=> đáp ứng yêu cầu responsive webpage

PS: lý tưởng
khi sử dụng max-width và margin:auto (căn element giua trang web)


<!DOCTYPE html>
<html>
<head>
<style>
div.ex1 {
    width:500px;
    margin: auto;
    border: 3px solid #73AD21;
}

div.ex2 {
    max-width:500px;
    margin: auto;
    border: 3px solid #73AD21;
}
</style>
</head>
<body>

<div class="ex1">This div element has width: 500px;</div>
<br>

<div class="ex2">This div element has max-width: 500px;</div>

<p><strong>Tip:</strong> Drag the browser window to smaller than 500px wide, to see the difference between 
the two divs!</p>

</body>
</html>

Wednesday, September 13, 2017

display:none/block/inline

The display property is the most important CSS property for controlling layout.

The display Property

The display property specifies if/how an element is displayed.
Every HTML element has a default display value depending on what type of element it is. The default display value for most elements is block or inline.

Click to show panel

This panel contains a <div> element, which is hidden by default (display: none).
It is styled with CSS, and we use JavaScript to show it (change it to (display: block).

Block-level Elements

A block-level element always starts on a new line and takes up the full width available (stretches out to the left and right as far as it can).

The <div> element is a block-level element.

Examples of block-level elements:

<div>
<h1> - <h6>
<p>
<form>
<header>
<footer>
<section>

Inline Elements

An inline element does not start on a new line and only takes up as much width as necessary.
This is an inline <span> element inside a paragraph.
Examples of inline elements:

<span>
<a>
<img>

Display: none;

display: none; is commonly used with JavaScript to hide and show elements without deleting and recreating them. Take a look at our last example on this page if you want to know how this can be achieved.
The <script> element uses display: none; as default.

Override The Default Display Value

As mentioned, every element has a default display value. However, you can override this.
Changing an inline element to a block element, or vice versa, can be useful for making the page look a specific way, and still follow the web standards.
A common example is making inline <li> elements for horizontal menus:

Example

li {
display: inline;}

Note: Setting the display property of an element only changes how the element is displayed, NOT what kind of element it is. So, an inline element with display: block; is not allowed to have other block elements inside it.

The following example displays <span> elements as block elements:

Example

span {
display: block;}

The following example displays <a> elements as block elements:

Example

a {
display: block;}

Hide an Element - display:none or visibility:hidden?

Hiding an element can be done by setting the display property to none. The element will be hidden, and the page will be displayed as if the element is not there:

Example

h1.hidden {
display: none;}

visibility:hidden; also hides an element.
However, the element will still take up the same space as before. The element will be hidden, but still affect the layout:

Example

h1.hidden {
visibility: hidden;}

visibility:hidden and display:none

display:none means that the tag in question will not appear on the page at all (although you can still interact with it through the dom). There will be no space allocated for it between the other tags.
visibility:hidden means that unlike display:none, the tag is not visible, but space is allocated for it on the page. The tag is rendered, it just isn't seen on the page.
For example:

test | <span style="[style-tag-value]">Appropriate style in this tag</span> | test

Replacing [style-tag-value] with display:none results in:

test |   | test

Replacing [style-tag-value] with visibility:hidden results in:

test |                        | test

Tuesday, September 12, 2017

CSS Links ( a:hover MUST come after a:link and a:visited a:active MUST come after a:hover)

links can be styled differently depending on what state they are in.
The four links states are:

a:link - a normal, unvisited link
a:visited - a link the user has visited
a:bay lượn - a link when the user mouses over it
a:active - a link the moment it is clicked

Example

/* unvisited link */
a:link {
    color: red;}

/* visited link */
a:visited {
    color: green;}

/* mouse over link */
a:hover {
    color: hotpink;}

/* selected link */
a:active {
    color: blue;}

When setting the style for several link states, there are some order rules:

a:hover MUST come after a:link and a:visited
a:active MUST come after a:hover

Ky thuat thiet lap co chu hien thi giong nhau tren tat ca trinh duyet

Use a Combination of Percent and Em

The solution that works in all browsers, is to set a default font-size in percent for the <body> element:

Example

body {
    font-size: 100%;}

h1 {
    font-size: 2.5em;}

h2 {
    font-size: 1.875em;}

p {
    font-size: 0.875em;}

Our code now works great! It shows the same text size in all browsers, and allows all browsers to zoom or resize the text!

Set Font Size With Em

To allow users to resize the text (in the browser menu), many developers use em instead of pixels.
The em size unit is recommended by the W3C.
1em is equal to the current font size. The default text size in browsers is 16px. So, the default size of 1em is 16px.
The size can be calculated from pixels to em using this formula: pixels/16=em

font-family

The font family of a text is set with the font-family property.
The font-family property should hold several font names as a "dự phòng" system. If the browser does not support the first font, it tries the next font, and so on.
Start with the font you want, and end with a generic family, to let the browser pick a similar font in the generic family, if no other fonts are available.
Note: If the name of a font family is more than one word, it must be in quotation marks, like: "Times New Roman".
More than one font family is specified in a comma-separated list:

Example

p {
font-family: "Times New Roman", Times, serif;}

text-align:justify (can thang hang cac dong)

CSS Box Model

All HTML elements can be considered as boxes. In CSS, the term "box model" is used when talking about design and layout.
The CSS box model is essentially a box that wraps around every HTML element. It consists of: margins, borders, padding, and the actual content. The image below illustrates the box model:

Explanation of the different parts:

Content - The content of the box, where text and images appear
Padding - Clears an area around the content. The padding is transparent
Border - A border that goes around the padding and content
Margin - Clears an area outside the border. The margin is transparent

The box model allows us to add a border around elements, and to define space between elements.

max-width=XXX (thieets lap de hien thi dung tren cac cua so nho - sao cho không có horizontal bar - thanh trượt ngang)

The max-width property is used to set the maximum width of an element.
The max-width can be specified in length values, like px, cm, etc., or in percent (%) of the containing block, or set to none (this is default. Means that there is no maximum width).
The problem with the <div> above occurs when the browser window is smaller than the width of the element (500px). The browser then adds a horizontal scrollbar to the page.
Using max-width instead, in this situation, will improve the browser's handling of small windows.
Tip: Drag the browser window to smaller than 500px wide, to see the difference between the two divs!

This element has a height of 100 pixels and a max-width of 500 pixels.

Note: The value of the max-width property overrides width.
The following example shows a <div> element with a height of 100 pixels and a max-width of 500 pixels:

Example

div {
    max-width: 500px;
    height: 100px;
    background-color: powderblue;}

Monday, September 11, 2017

margin=auto (căn giua )

you can set the margin property to auto to horizontally center the element within its container.
The element will then take up the specified width, and the remaining space will be split equally between the left and right margins:

Example

div {
    width: 300px;
    margin: auto;
    border: 1px solid red;}

Sunday, September 10, 2017

Three Ways to Insert CSS & Cascading Order

Three Ways to Insert CSS

There are three ways of inserting a style sheet:

External style sheet
Internal style sheet
Inline style

External Style Sheet

With an external style sheet, you can change the look of an entire website by changing just one file!
Each page must include a reference to the external style sheet file inside the <link> element. The <link> element goes inside the <head> section:

Example

An external style sheet can be written in any text editor. The file should not contain any html tags. The style sheet file must be saved with a .css extension.
Here is how the "mystyle.css" looks:

body {
    background-color: lightblue;}

h1 {
    color: navy;
    margin-left: 20px;}

Note: Do not add a space between the property value and the unit (such as margin-left: 20 px;). The correct way is: margin-left: 20px;

Internal Style Sheet

An internal style sheet may be used if one single page has a unique style.
Internal styles are defined within the <style> element, inside the <head> section of an HTML page:

Example

<head>
<style>
body {
    background-color: linen;}

h1 {
    color: maroon;
    margin-left: 40px;}
</style>
</head>

Inline Styles

An inline style may be used to apply a unique style for a single element.
To use inline styles, add the style attribute to the relevant element. The style attribute can contain any CSS property.
The example below shows how to change the color and the left margin of a <h1> element:

Example

<h1 style="color:blue;margin-left:30px;">This is a heading</h1>

Tip: An inline style loses many of the advantages of a style sheet (by mixing content with presentation). Use this method sparingly.

Multiple Style Sheets

If some properties have been defined for the same selector (element) in different style sheets, the value from the last read style sheet will be used.

Example

Assume that an external style sheet has the following style for the <h1> element:

h1 {
color: navy;
}

then, assume that an internal style sheet also has the following style for the <h1> element:

h1 {
color: orange; }

If the internal style is defined after the link to the external style sheet, the <h1> elements will be "orange":

Example

<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
<style>
h1 {
color: orange;}</style>
</head>

However, if the internal style is defined before the link to the external style sheet, the <h1> elements will be "navy":

Example

<head>
<style>
h1 {
color: orange;}</style>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>

Cascading Order

What style will be used when there is more than one style specified for an HTML element?
Generally speaking we can say that all the styles will "thác nước" into a new "virtual" style sheet by the following rules, where number one has the highest priority:

Inline style (inside an HTML element)
External and internal style sheets (in the head section)
Browser default

So, an inline style (inside a specific HTML element) has the highest priority, which means that it will override a style defined inside the <head> tag, or in an external style sheet, or a browser default value.

/* Css comment */

Comments are used to explain the code, and may help when you edit the source code at a later date.
Comments are ignored by browsers.
A CSS comment starts with /* and ends with */. Comments can also span multiple lines:

Example

p {
    color: red;
    /* This is a single-line comment */
    text-align: center;
}

/* This is
a multi-line
comment */

CSS Syntax and Selectors

CSS Syntax

A CSS rule-set consists of a selector and a declaration block:
CSS selector

The selector points to the HTML element you want to style.
The declaration block contains one or more declarations separated by semicolons.
Each declaration includes a CSS property name and a value, separated by a colon.
A CSS declaration always ends with a semicolon, and declaration blocks are surrounded by curly braces.
In the following example all <p> elements will be center-aligned, with a red text color:

Example

p {
color: red;
text-align: center;
}

CSS Selectors

CSS selectors are used to "find" (or select) HTML elements based on their element name, id, class, attribute, and more.

The element Selector

The element selector selects elements based on the element name.
You can select all <p> elements on a page like this (in this case, all <p> elements will be center-aligned, with a red text color):

Example

p {
text-align: center;
color: red;
}

The id Selector

The id selector uses the id attribute of an HTML element to select a specific element.
The id of an element should be unique within a page, so the id selector is used to select one unique element!
To select an element with a specific id, write a hash (#) character, followed by the id of the element.
The style rule below will be applied to the HTML element with id="para1":

Example

#para1 {
text-align: center;
color: red;
}

Note: An id name cannot start with a number!

The class Selector

The class selector selects elements with a specific class attribute.
To select elements with a specific class, write a period (.) character, followed by the name of the class.
In the example below, all HTML elements with class="center" will be red and center-aligned:

Example

.center {
text-align: center;
color: red;}

You can also specify that only specific HTML elements should be affected by a class.
In the example below, only <p> elements with class="center" will be center-aligned:

Example

p.center {
text-align: center;
color: red;}

HTML elements can also refer to more than one class.
In the example below, the <p> element will be styled according to class="center" and to class="large":

Example

<p class="center large">This paragraph refers to two classes.</p>

Note: A class name cannot start with a number!

Grouping Selectors

If you have elements with the same style definitions, like this:

h1 {
    text-align: center;
    color: red;
}

h2 {
    text-align: center;
    color: red;}

p {
    text-align: center;
    color: red;
}

It will be better to group the selectors, to minimize the code.
To group selectors, separate each selector with a comma.
In the example below we have grouped the selectors from the code above:

Example

h1, h2, p {
text-align: center;
color: red;}

CSS Introduction

What is CSS?

CSS stands for Cascading Style Sheets
CSS describes how HTML elements are to be displayed on screen, paper, or in other media
CSS saves a lot of work. It can control the layout of multiple web pages all at once
External stylesheets are stored in CSS files

CSS Demo - One HTML Page - Multiple Styles!

Here we will show one HTML page displayed with four different stylesheets. Click on the "Stylesheet 1", "Stylesheet 2", "Stylesheet 3", "Stylesheet 4" links below to see the different styles:

Why Use CSS?

CSS is used to define styles for your web pages, including the design, layout and variations in display for different devices and screen sizes.

CSS Solved a Big Problem

HTML was NEVER intended to contain tags for formatting a web page!
HTML was created to describe the content of a web page, like:
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
When tags like <font>, and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large websites, where fonts and color information were added to every single page, became a long and expensive process.
To solve this problem, the World Wide Web Consortium (W3C) created CSS.
CSS removed the style formatting from the HTML page!

CSS Saves a Lot of Work!

The style definitions are normally saved in external .css files.
With an external stylesheet file, you can change the look of an entire website by changing just one file!

Saturday, September 9, 2017

Layout với div (block element) và span(inline element)

Every HTML element has a default display value depending on what type of element it is. The default display value for most elements is block or inline.

Block-level Elements

A block-level element always starts on a new line and takes up the full width available (trải dài ra to the left and right as far as it can).

The <div> element is a block-level element.

Examples of block-level elements:

<div>
<h1> - <h6>
<p>
<form>

Inline Elements

An inline element does not start on a new line and only takes up as much width as necessary.
This is an inline <span> element inside a paragraph.
Examples of inline elements:

<span>
<a>
<img>

The <div> Element

The <div> element is often used as a container for other HTML elements.
The <div> element has no required attributes, but both style and class are common.
When used together with CSS, the <div> element can be used to style blocks of content:

Example

<div style="background-color:black;color:white;padding:20px;">
<h2>London</h2>
<p>London is the capital city of England. It is the most populous city in the United Kingdom, with a metropolitan area of over 13 million inhabitants.</p>
</div>

The <span> Element

The <span> element is often used as a container for some text.
The <span> element has no required attributes, but both style and class are common.
When used together with CSS, the <span> element can be used to style parts of the text:

Example

<h1>My <span style="color:red">Important</span> Heading</h1>

Tạo menu với css và unorder list ul

HTML lists can be styled in many different ways with CSS.
One popular way is to style a list horizontally, to create a menu:

Ví dụ 1:


<!DOCTYPE html>

<html>

<head>

<style>

ul#menu {

    list-style-type: none;

    margin: 0;

    padding: 0;

}



ul#menu li {

    float:left;

}

</style>

</head>

<body>



<ul id="menu">

  <li>Apples</li>

  <li>Bananas</li>

  <li>Lemons</li>

  <li>Oranges</li>

</ul>  



</body>

</html>

Ví dụ 2:


<!DOCTYPE html>
<html>
<head>
<style>
ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    background-color: #888888;
}

li {
    float: left;
}

li a {
    display: block;
    color: white;
    text-align: center;
    padding: 16px;
    text-decoration: none;
}

li a:hover {
    background-color: #111111;
}
</style>
</head>
<body>

<ul>
  <li><a href="#home">Home</a></li>
  <li><a href="#news">News</a></li>
  <li><a href="#contact">Contact</a></li>
  <li><a href="#about">About</a></li>
</ul>

</body>
</html>

HTML Styles - CSS

CSS = Styles and Colors

Manipulate Text

Colors, Boxes

Styling HTML with CSS

CSS stands for Cascading Style Sheets.
CSS describes how HTML elements are to be displayed on screen, paper, or in other media.
CSS saves a lot of work. It can control the layout of multiple web pages all at once.
CSS can be added to HTML elements in 3 ways:

Inline - by using the style attribute in HTML elements
Internal - by using a <style> element in the <head> section
External - by using an external CSS file

The most common way to add CSS, is to keep the styles in separate CSS files. However, here we will use inline and internal styling, because this is easier to demonstrate, and easier for you to try it yourself.

Tip: You can learn much more about CSS in our CSS Tutorial.

Inline CSS

An inline CSS is used to apply a unique style to a single HTML element.
An inline CSS uses the style attribute of an HTML element.
This example sets the text color of the <h1> element to blue:

Example

<h1 style="color:blue;">This is a Blue Heading</h1>

Internal CSS

An internal CSS is used to define a style for a single HTML page.
An internal CSS is defined in the <head> section of an HTML page, within a <style> element:

Example

<!DOCTYPE html>
<html>
<head>
<style>
body {background-color: powderblue;}
h1 {color: blue;}
p {color: red;}
</style>
</head>
<body>

<h1>This is a heading</h1>
<p>This is a paragraph.</p>

</body>
</html>

External CSS

An external style sheet is used to define the style for many HTML pages.
With an external style sheet, you can change the look of an entire web site, by changing one file!
To use an external style sheet, add a link to it in the <head> section of the HTML page:

Example

<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="styles.css">
</head>
<body>

<h1>This is a heading</h1>
<p>This is a paragraph.</p>

</body>
</html>

An external style sheet can be written in any text editor. The file must not contain any HTML code, and must be saved with a .css extension.
Here is how the "styles.css" looks:

body {
    background-color: powderblue;}
h1 {
    color: blue;}
p {
    color: red;}

CSS Fonts

The CSS color property defines the text color to be used.
The CSS font-family property defines the font to be used.
The CSS font-size property defines the text size to be used.

Example

<!DOCTYPE html>
<html>
<head>
<style>
h1 {
    color: blue;
    font-family: verdana;
    font-size: 300%;}
p {
    color: red;
    font-family: courier;
    font-size: 160%;}</style>
</head>
<body>

<h1>This is a heading</h1>
<p>This is a paragraph.</p>

</body>
</html>

CSS Border

The CSS border property defines a border around an HTML element:

Example

p {
border: 1px solid powderblue;}

CSS Padding

The CSS padding property defines a padding (space) between the text and the border:

Example

p {
border: 1px solid powderblue;
padding: 30px;}

CSS Margin

The CSS margin property defines a margin (space) outside the border:

Example

p {
border: 1px solid powderblue;
margin: 50px;
}

The id Attribute

To define a specific style for one special element, add an id attribute to the element:

<p id="p01">I am different</p>

then define a style for the element with the specific id:

Example

#p01 {
color: blue;}

Note: The id of an element should be unique within a page, so the id selector is used to select one unique element!

The class Attribute

To define a style for a special type of elements, add a class attribute to the element:

<p class="error">I am different</p>

then define a style for the elements with the specific class:

Example

p.error {
color: red;}

External References

External style sheets can be referenced with a full URL or with a path relative to the current web page.
This example uses a full URL to link to a style sheet:

Example

This example links to a style sheet located in the html folder on the current web site:

Example

This example links to a style sheet located in the same folder as the current page:

Example

You can read more about file paths in the chapter HTML File Paths.

Chapter Summary

Use the HTML style attribute for inline styling
Use the HTML <style> element to define internal CSS
Use the HTML <link> element to refer to an external CSS file
Use the HTML <head> element to store <style> and <link> elements
Use the CSS color property for text colors
Use the CSS font-family property for text fonts
Use the CSS font-size property for text sizes
Use the CSS border property for borders
Use the CSS padding property for space inside the border
Use the CSS margin property for space outside the border