<select onchange="location.href='chek.asp?keyword='+this.value">
<option value="a1">值1</option>
<option value="a2">值2</option>
</select>


<form name="frm1" mothod=get>
<select name=sele>
<option value="a1">值1</option>
<option value="a2">值2</option>
</select></form><a href=# onclick=location.href='chek.asp?

keyword='+frm1.sele.value>进 行 测 试</a>