function createRequestObject() 
     {
	  var ro;
	  var browser = navigator.appName;
	  if(browser == "Microsoft Internet Explorer")
	  {
	   ro = new ActiveXObject("Microsoft.XMLHTTP");
	  }else
	  {
	   ro = new XMLHttpRequest();
	  }
	  return ro;
     }
    var http=createRequestObject();
    function validateuserid()
    {
    var target=document.getElementById("uname").value;
    var url="validate.jsp?keyword="+target; 
    http.open('get', url);
		http.onreadystatechange = callback;
		http.send(null);
    }
    function callback(){
    if(http.readyState == 4)
	{
		try
		{
			
			document.getElementById('userIdMessage').innerHTML = http.responseText;
		} // end try 
		catch(e)
		{
			alert("Error: " + e) ;
		} // end try catch
	} // end if readystate 4
    }