<html><head><script type="text/javascript" src="/jquery/jquery.js"></script><script type="text/javascript">$(document).ready(function(){ $("button").click(function(){ $("#id200").width("300px"); });});</script></head><body><div id="id100" style="background:yellow;height:100px;width:100px">HELLO</div><div id="id200" style="background:yellow;height:100px;width:100px">W3SCHOOL</div><button type="button">请点击这里</button></body></html>