function doCallAjax() {
	
var txtUser = document.getElementById("txtUser").value;

		var req;
				if(window.XMLHttpRequest) req = new XMLHttpRequest(); 
				else if(window.ActiveXObject) req = new ActiveXObject("Microsoft.XMLHTTP");
				else { 
					alert("Browser not support"); return false; 
				}
				
				req.onreadystatechange = function() 
				 {
						if(req.readyState == 4) {
							var x = document.getElementById("mySpan");
								x.innerHTML = req.responseText;	
						} else {	
							var x = document.getElementById("mySpan");
							x.innerHTML = '<div align="center"><img src="images/indicator.gif" /></div>';
						}
				  }
				
					var str = Math.random();
					var querystr = ""; 
					querystr+="2.php?sessId="+str;
					
					var Data = " ";
					Data += "txtUser="+txtUser;
					req.open("POST",querystr,true);
					
					req.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
					req.setRequestHeader("Content-length", Data.length);
					req.send(Data);		
}