我建议添加overflow：hidden; （和zoom：1;为了保持IE6的跨浏览器兼容性）到容器div，而不是添加一个清除div。 Clear为您的源代码添加了膨胀。

I'd recommend adding overflow:hidden; (and zoom: 1; to maintain cross browser compatability for IE6) to the container div rather than adding a clearing div. Clear adds bloat to your source code.

#container #header-usernav ul {
    list-style: none;
    padding: 0;
    margin: 0;
    margin-left: 10px;
    overflow: hidden;
    zoom: 1;
    height: 28px; /* This is needed to ensure that the height of the rounded corners matches up with the rest of the bg.
}