var xmlHttp;
		
		function performCheck()
		{		
			xmlHttp = GetXmlHttpObject();			
			
			if (xmlHttp == null)
			{
				alert ("Browser does not support HTTP Request");
				return;
			}
			var url = "perform_check.php";	
						
			url = url+"?sid="+Math.random();
			//alert(url);
			xmlHttp.onreadystatechange = stateChanged;
			xmlHttp.open("GET",url,true);
			xmlHttp.send(null);
		}
		
		function stateChanged() 
		{ 
		if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
		 { 
		  	 //alert("Duomenys gauti");
		  	 //alert(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;
		}