方法1：
<form id="form1" name="form1" method="post" action="../news/index.asp">
<table width="100%" height="43" border="0" cellpadding="0" cellspacing="0">
<tr>
<td height="28"><input name="keyword" type="text" style="150px" id="keyword"/></td>
</tr>
<tr>
<td height="28"><select name="Searchtype" style="110px" id="Searchtype" onchange="Searchtype1();">
<option value="news" selected="selected">新闻中心</option>
<option value="case">工程案例</option>
</select>
<input type="submit" name="Submit" value="搜索" /></td>
</tr>
</table>
</form>
<script language="javascript">
function Searchtype1(){
var type=document.getElementById("Searchtype").options[document.getElementById("Searchtype").selectedIndex].value;
if (type=="news"){document.getElementById("form1").action="../news/index.asp"}
else if (type=="case"){document.getElementById("form1").action="../case/index.asp"}
}
</script>
方法2：
<html>
<head>
<script language="javascript">
function check(){
if(document.form1.a[0].checked==true)
document.form1.action="1.htm"
else
document.form1.action="2.htm"
}
</script>
</head>
<body>
<form name="form1" method="post" action="" onSubmit="check();">
转到页面一<input type="radio" name="a">
转到页面二<input type="radio" name="a">
<input name="" type="submit" value="提交">
</form>
</body>
</html>