function search()
{  
   var s=document.getElementById("txtsearch").value;
   if(s != "")
   {   
       window.document.location.href="search.aspx?s="+window.encodeURIComponent(s);
   }
}
function submitByEnter(e) {
 e = e || window.event;
 var key = e ? (e.charCode || e.keyCode) : 0;
  
     if(key == 13) {
       document.getElementById("btnSeach").focus();
       search();
    }
}

function listen() {
 var aa = document.getElementById('txtsearch');
 try{
   document.addEventListener('keydown', submitByEnter, true);
 } catch(ex) {

   document.attachEvent('onkeydown', submitByEnter);
 }
}
window.onload=listen;