CSS 对齐方式

居中设置

Center Align - Using margin

Setting the width of a block-level element will prevent it from stretching out to the edges of its container. Use margin: auto;, to horizontally center an element within its container.

The element will then take up the specified width, and the remaining space will be split equally between the two margins:

<!DOCTYPE html>
<html>
<head>
<style>
.center {
    margin: auto;
    width: 60%;
    border: 3px solid #73AD21;
    padding: 10px;
}
</style>

<script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "//hm.baidu.com/hm.js?73c27e26f610eb3c9f3feb0c75b03925";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
</head>
<body>

<div class="center">
  <p><b>Note: </b>Using margin:auto will not work in IE8, unless a !DOCTYPE is declared.</p>
</div>

</body>
</html>

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Tip: Center aligning has no effect if the width property is not set (or set to 100%).

Tip: For aligning text, see the CSS Text chapter.

Left and Right Align - Using position

One method for aligning elements is to use position: absolute;:

<!DOCTYPE html>
<html>
<head>
<style>
.right {
    position: absolute;
    right: 0px;
    width: 300px;
    border: 3px solid #73AD21;
    padding: 10px;
}
</style>

<script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "//hm.baidu.com/hm.js?73c27e26f610eb3c9f3feb0c75b03925";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
</head>
<body>

<div class="right">
  <p>In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.</p>
</div>

</body>
</html>

View Code

Note: Absolute positioned elements are removed from the normal flow, and can overlap elements.

Tip: When aligning elements with position, always define margin and padding for the <body> element. This is to avoid visual differences in different browsers.

There is also a problem with IE8 and earlier, when using position. If a container element (in our case <div class="container">) has a specified width, and the !DOCTYPE declaration is missing, IE8 and earlier versions will add a 17px margin on the right side. This seems to be space reserved for a scrollbar. So, always set the !DOCTYPE declaration when using position:

Left and Right Align - Using float

Another method for aligning elements is to use the float property:

<!DOCTYPE html>
<html>
<head>
<style>
.right {
    position: absolute;
    right: 0px;
    width: 300px;
    border: 3px solid #73AD21;
    padding: 10px;
}
</style>

<script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "//hm.baidu.com/hm.js?73c27e26f610eb3c9f3feb0c75b03925";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
</head>
<body>

<div class="right">
  <p>In my younger and more vulnerable years my father gave me some advice that I've been turning over in my mind ever since.</p>
</div>

</body>
</html>

View Code