Some css position box description

1. padding:

What would happen if you used either ems or percentages for the padding values?
The two units have slightly different effects: the em unit scales the padding according
to the size of the font of the content, while the percentage unit scales
the padding (and margin) according to the width or height of the block that contains the element.

 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Box Model Demo</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <style type="text/css">
        body
        {
            background-color: #808080;
            color: black;
        }
        h1, h4
        {
            background-color: #c0c0c0;
            color: black;
            padding: 10%;
        }
        
        .main-div 
        {
            width: 600px;
            height: 300px;
        }
    </style>
</head>
<body>
    <div class="main-div">
    
    <h1>
        MMMMMM</h1>
    <h4>
        MMMMMM</h4>
    </div>
</body>
</html>

the above html fragment shows H1 and H4 has 10% padding, their parent container DIV's width is 600px so their padding will be 60px.

If change the H1 H4 css style to  use em like

h1, h4
        {
            background-color: #c0c0c0;
            color: black;
            padding: 1em;
        }

then in IE browse the H1 padding will be 32px and h4 padding will be 16px.

2. absolute

The absolute position will calc by it's parent:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Box Model Demo</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <style type="text/css">
        .big
        {
            font-family: Helvetica, Arial, sans-serif;
            font-size: 2em;
            font-weight: bold;
        }
    </style>
</head>
<body>
    <div style="position: absolute; left: 125px; top: 75px;" class="big">
        This is the first line of text being positioned.
        <div style="position: absolute; left: 25px; top: 30px;" class="big">
            This is a second line.
        </div>
    </div>
</body>
</html>

　　

3. relative

Relative positioning is always based on the positioned element’s original position on the page.

In other words, the positioning context of an element that uses relative positioning is provided by its default position.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Box Model Demo</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <style type="text/css">
        .big
        {
            font-family: Helvetica, Arial, sans-serif;
            font-size: large;
            font-weight: bold;
        }
    </style>
</head>
<body>
    <div style="position: absolute; left: 125px; top: 75px;" class="big">
        This is the first line of text being positioned.
        <div style="position: absolute; left: 25px; top: 30px;">
            This is <span style="position: relative; left: 10px; top: 30px;">an example of</span>
            a second line.
        </div>
    </div>
</body>
</html>

　　

 

posted on 2012-07-21 20:12  dragonstreak_1  阅读(181)  评论(0)  编辑  收藏  举报

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