左侧固定，右侧自适应，是一种很常见的布局，经常会见到

<div class="wrap" id="wrap">
    <div class="wrap-left">left</div>
    <div class="wrap-right">right</div>
</div>

.wrap { width: 600px; border: 2px solid #ff0000; }
.wrap-left { height: 200px; float: left; width: 100px; background: #ffd800; }
.wrap-right { height: 200px; margin-left: 100px; background: #b6ff00; }