阿立的做法
http://blog.miniasp.com/post/2008/02/03/Avoid-browser-cache-problem-on-css-or-javascript-file.aspx
http://stackoverflow.com/questions/4670738/clear-cached-javascript-includes-in-firefox
code：
<script type="text/javascript" src="js/extjs/mygrid.js?x=<%= (int) (Math.random() * 10000) %>"></script>