////////////////////////////////////////Check Username Availability/////////////////////////////
function check_username()
{
	var username=document.getElementById('username').value;
	document.getElementById("username_message").innerHTML='';
	
	if(username.length==0)
	{			
		document.getElementById("username_message").innerHTML="<font color='red'>Please Enter Username</font>";
		//document.getElementById('username').focus();
		return false;
	}
	
	if(username.match(/[^a-zA-Z0-9_]/))
	{
		document.getElementById("username_message").innerHTML="<font color='red'>Username may contain only alphanumeric and underscore characters</font>";
		//document.getElementById('username').focus();
		return false;
	}
	
	
	xmlHttp=UserGetXmlHttpObject()
	if (xmlHttp==null)
  	{
  		alert ("Your browser does not support AJAX!");
  		return;
  	} 
  
  		var url="../includes/ajax/check_user_name.php";
		url=url+"?username="+username;
		url=url+"&sid="+Math.random();
		xmlHttp.onreadystatechange=UserStateChanged;
		xmlHttp.open("GET",url,true);
		xmlHttp.send(null);
 
}
	
	
function UserStateChanged() 
{ 
	if (xmlHttp.readyState==4)
	{ 
		var response=xmlHttp.responseText;
		if(response==1)
		{
			return true;			
			//document.getElementById("registration").submit();
		}
		
		if(response==0)
		{
			//alert("STOP");
			document.getElementById("username_message").innerHTML="<font color='red'>Username Already Exists Try Another</font>";
			//document.getElementById('username').focus();
			return false;
		}

	}
}
 

function UserGetXmlHttpObject()
{
	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;
}