<form name="f">
<select name="s">
<option></option>
<option></option>
<option></option>
</select>
<input type="reset" value="Select无效" onclick="f.s.disabled=true;" />
</form>
<select name="s">
<option></option>
<option></option>
<option></option>
</select>
<input type="reset" value="Select无效" onclick="f.s.disabled=true;" />
</form>
<FORM name="form1" method="post" action="">
<SELECT name="sel">
<OPTION>aaa</OPTION>
<OPTION>aaa</OPTION>
<OPTION>aaa</OPTION>
<OPTION>aaa</OPTION>
</SELECT>
</FORM>
</BODY>
<select name="s1">
<option>aaa</option>
<option>bbb</option>
<option>ccc</option>
</select>
<input type="button" value="test" onclick="s1.disabled=!s1.disabled" />