51help TIY
码：
<html> <head> <style type="text/css"> p { border: thin dotted #FF0000; } </style> <script type="text/javascript"> function changeBorder() { document.getElementById("p1").style.borderBottom="thick solid blue"; } </script> </head> <body> <input type="button" onclick="changeBorder()" value="Change bottom border" /> <p id="p1">This is a paragraph with a border</p> </body> </html>
查看结果: