function getXMLHTTP() { //fuction to return the xml http object
		var xmlhttp=false;	
		try{
			xmlhttp=new XMLHttpRequest();
		}
		catch(e)	{		
			try{			
				xmlhttp= new ActiveXObject("Microsoft.XMLHTTP");
			}
			catch(e){
				try{
				xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
				}
				catch(e1){
					xmlhttp=false;
				}
			}
		}
		 	
		return xmlhttp;
	}


function chk_user_avail(value,div_id,ext_file,type) {		
var req = getXMLHTTP();
var url=ext_file
url=url+"?val="+value
url=url+"&type="+type
url=url+"&sid="+Math.random()
if (req) {		
		req.onreadystatechange = function() {
			if (req.readyState == 4) {
				if (req.status == 200) {						
					document.getElementById(div_id).innerHTML=req.responseText;						
				} else {
					alert("There was a problem while using XMLHTTP:\n" + req.statusText);
				}
			}				
		}			
		req.open("GET", url, true);
		req.send(null);
	}
			
}