Cross-browser practice: fixed positioning of position:fixed layer_Experience exchange

Look at the example:

HTML example:

<!-- quirksmode --><title>Demo</title> <link href="fixed.css" rel="stylesheet" type="text/css"> <div id="menu"> Mozilla Opera Netscape Firefox IE6 Windows Style CSS </div> <div id="content"> As long as the content is larger than the height of one screen </div>
[Ctrl A Select all Note:If you need to introduce external Js, you need to refresh it before it can be executed]

Can you delete the first line of comments and see what the effect is?