var xmlHttp
function CheckUser(str){
xmlHttp=GetXmlHttpObject()
	if (xmlHttp==null){
 		alert ("Browser does not support HTTP Request")
 		return
 	}
var url="ajax_check_user_name.php"
url=url+"?q="+str
url=url+"&sid="+Math.random()
xmlHttp.onreadystatechange=stateChanged
xmlHttp.open("GET",url,true)
xmlHttp.send(null)
}

function stateChanged()
{
var flag;
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
// document.getElementById("txtHint").innerHTML=xmlHttp.responseText;
 flag=xmlHttp.responseText;
 //alert(flag);
 if(flag==0)
 {
     //alert("it is correct");
	 document.getElementById("send").disabled=false;
 }
if(flag==1)
 {
      alert("enter valid user name");
     document.getElementById("send").disabled=true;
 }
 }
}

function GetXmlHttpObject(){
var xmlHttp=null;
try{
 // Firefox, Opera 8.0+, Safari
 xmlHttp=new XMLHttpRequest();
 }
catch (e){
 //Internet Explorer
 try {
  xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
  }
 catch (e){
  xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
 }
return xmlHttp;
}