var xmlHttp

function check_username1(url)
{
	 
	xmlHttp=GetXmlHttpObject()
	if (xmlHttp==null)
	  {
		  alert ("Browser does not support HTTP Request")
		  return
	  } 	
	var username = document.getElementById("username").value 
	var url = "chk_username.php"
	url=url+"?username="+username
	xmlHttp.onreadystatechange=stateChanged_username 
	xmlHttp.open("GET",url,true)
	xmlHttp.send(null)
} 

function stateChanged_username() 
{ 
	if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
	 { 
	 	
		document.getElementById("username_available").innerHTML=xmlHttp.responseText 
		  
	 } 
	 
}

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;
}