.header{
width:100%;
height:100px;
background:red;
color:#333333;
}
<div class="header">
aaaaaaaaaaaaaaeeeeeeeeeeeeeeeeeeeeeeddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddssssssssssssssssssssssssssssssssqqqqqqqqqqqqqq
</div>
这样写样式，会造成当页面缩小时，向右拉动滚动条，发现右边有空白。
解决办法，（不支持ie6及以下版本）：body{min-width:1000px;}