var xmlHttp
      var msg
      function GetXmlHttpObject()
        { 
          var objXMLHttp=null
          if (window.XMLHttpRequest)
          {
            objXMLHttp=new XMLHttpRequest()
			thibrow = 1;
          }
          else if (window.ActiveXObject)
          {
            objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
			thibrow =0;
          }
          return objXMLHttp
        }
        
      
        
      xmlHttp=GetXmlHttpObject()
      
      if (xmlHttp==null)
      {
        alert ("Browser does not support HTTP Request");
      } 
      else { 
      
        function stateChanged_AVAIL() 
        { 
          if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
          { 
            var text = xmlHttp.responseText
            var arr = xmlHttp.responseText.split('&')
           // alert(text);
			
            /* for check purpose */
			if(arr[0] == "avail")
            {
            	if(arr[1] == '1')
            	{
            		document.getElementById("chkavail").innerHTML= "<font color='green'>Username " + document.getElementById('txtusername').value + " is available! You can proceed.</font>";
            	}
            	else
            	{
            		document.getElementById("chkavail").innerHTML= "<font color='red'>Username " + document.getElementById('txtusername').value + " is not available!</font>";
            	}
            }

            /* end of check */
          }
		  
        }   
        
        function check_username()
        {
        	var url = "check_availability.php"
          url=url+"?username="+ document.getElementById('txtusername').value
          xmlHttp.onreadystatechange=stateChanged_AVAIL;
          xmlHttp.open("GET",url,true);
          xmlHttp.send(null); 
        }
        
}