求助高手，调用的函数不起作用

function Assort_Select(assObj){ //当更改新闻类别后，仅显示该类的新闻
var a=assObj.options[assObj.selectedIndex].value;
if (a!=""){
var url="?Assort_id="+a;
window.navigate(url);}
}
<select name="select" onchange="Assort_Select(this)">
<%
Set rs=conn.Execute ("SELECT * FROM category")
if rs.EOF or rs.BOF Then
response.Write "<option>还没有任何新闻类别</option>"
elseresponse.Write "<option>全部新闻</option>"
do while not rs.eof
id=rs("categoryid")
response.Write "<option value=""" & id & """"
if assort_id=id then response.Write " selected"
response.Write">" & rs("categoryname") & "</option>"
rs.MoveNext
Loop
end if
rs.close
set rs=nothing
%></select>