function Change_Stadt(kategorie)
{
 var sel_kat_value = kategorie;
 var sel_stadt_value = document.staedteform.staedte.options[document.staedteform.staedte.selectedIndex].value;
 
 var URL = "http://" + location.host + location.pathname;
 var QueryParamKat="";
 var QueryParamStadt="";
 
 if (sel_kat_value!=0)
    QueryParamKat="kat_id=" + sel_kat_value;
 

 
 if (sel_stadt_value!="0")
   {
    if (QueryParamKat!="")
      QueryParamStadt="&"
    QueryParamStadt=QueryParamStadt + "stadt=" + sel_stadt_value;
   } 
 
 
 window.location.href = URL + "?" + QueryParamKat +  QueryParamStadt;
}