passing values to serverside getting values from severside to javascript

i have javascript  which is initated on gridheader click  function getHname() {  document.getElementById('HCELLVAL')= gridheadercell.value; document.getElementById('<%=gettype.ClientID %>').click(); alert(document.getElementById('H_TYPE').value); CopyToHiddenVar('<%=H_TYPE.Value %>'); } i get   document.getElementById('HCELLVAL') value  function CopyToHiddenVar(filterType)         {       alert( filterType); // this is blank i dont get any value         } on document.getElementById('<%=gettype.ClientID %>').click();  event on server side i get  the  TYPE from database depending on the headercell value which i am storing in a hidden variable on server side but here in client  not getting that value =========================================== on serverside  protected void gettype_Click(object sender, EventArgs e)         {      Storevalues();     H_TYPE.Value = ds.Tables[0].Rows[0]["TYPE"].ToString();           }  private void StoreLastFilterValue()         {             Hashtable filterCriteria = (Hashtable)Session["filterCriteria"];                        String[] selValues = FilterValue.Value.Split(',');             switch (FilterType.Value)             {         // i get FilterType.Value as blank              } }