左右结构，左边100%；右边宽度固定
css
#header{height:80px; background:#CCC;}
#center{overflow:hidden; zoom:1;}
#main_wrapper{float:left; width:100%; margin-top:10px; margin-left:-210px;}
#main{height:200px; margin-left:210px; background:#999;}
#sidebar{float:right; width:200px; margin-top:10px; height:200px; background:#AAA;}
#footer{height:50px; margin-top:10px; background:#CCC;}
HTML
<body>
<div id="header"></div>
<div id="center">
<div id="main_wrapper">
<div id="main"></div>
</div>
<div id="sidebar"></div>
</div>
<div id="footer"></div>
</body>
左右结构，左边固定，右边100%
css
#header{height:80px; background:#CCC;}
#center{overflow:hidden; zoom:1;}
#sidebar{float:left; width:200px; margin-top:10px; height:200px; background:#AAA;}
#main_wrapper{float:right; width:100%; margin-top:10px; margin-left:-210px;}
#main{height:200px; margin-left:210px; background:#999;}
#footer{height:50px; margin-top:10px; background:#CCC;}
html
<body>
<div id="header"></div>
<div id="center">
<div id="sidebar"></div>
<div id="main_wrapper">
<div id="main"></div>
</div>
</div>
<div id="footer"></div>
</body>
左中右结构，左边固定，右边固定，中间100%;
css
#header{height:80px; background:#CCC;}
#center{overflow:hidden; zoom:1;}
#sidebar-l {float:left; width:200px; margin-top:10px; height:200px; background:#AAA;}
#main-wrapper {margin-top:10px; float:left; width:100%; margin-left:-420px; height:200px;}
#main {margin-left:438px; background:#999; height:200px;}
#sidebar-r {float:right; width:200px; margin-top:10px; height:200px; background:#AAA;}
#footer{height:50px; margin-top:10px; background:#CCC;}
html
<body>
<div id="header"></div>
<div id="center">
<div id="sidebar-l">这里是左边</div>
<div id="main-wrapper">
<div id="main">这里是中间</div>
</div>
<div id="sidebar-r">这里是右边</div>
</div>
<div id="footer"></div>
</body>
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