网页布局，左固定右自适应宽

<style type="text/css">
    body {
        font: 12px arial;
        color: #000;
        background: #fff;
        margin: 0;
    }

    #header {
        height: 50px;
        color: #fff;
        background: #666;
        line-height: 50px;
        margin-bottom: 10px;
    }

    #right {
        width: 100%;
        color: #fff;
        float: right;
        margin-right: -240px;
    }

    #right_inner {
        height: 400px;
        background: #666;
        margin-right: 240px;
    }

    #left {
        width: 230px;
        height: 400px;
        color: #fff;
        background: #666;
        float: left;
    }

    #footer {
        height: 50px;
        color: #fff;
        background: #666;
        margin-top: 10px;
    }

    .clear {
        clear: both;
    }
</style>
</head>

<body>
    <div id="header">顶部</div>

    <div id="right">
        <div id="right_inner">右侧</div>
    </div>
    <div id="left">左侧</div>
    <div class="clear"></div>

    <div id="footer">底部</div>

另一种方法

<style type="text/css">
    body {
        margin: 0;
    }

    #container {
        margin-left: 230px;
        _zoom: 1;
        /*兼容IE6下左栏消失问题*/
    }

    #left {
        float: left;
        width: 230px;
        height: 600px;
        background: #ccc;
        margin-left: -230px;
        position: relative;
        /*兼容IE6下左栏消失问题，IE6真不让人省心啊>_<*/
    }

    #right {
        height: 400px;
        background: #0099ff;
    }

    #footer {
        clear: both;
        text-align: center;
        background: #009000;
    }
</style>
</head>
<body>
    <div id="container">
        <div id="left">
            左栏
        </div>
        <div id="right">
            右栏
        </div>
    </div>
    <div id="footer">
        底栏
    </div>