function validate_user_authandication()
{

	 URL="validate_user_authandication.php";
	 if(window.XMLHttpRequest)
		{
		  browser_request=new XMLHttpRequest();
		}
	 else if(window.ActiveXObject){
		//For IE 5
		browser_request = new ActiveXObject("Microsoft.XMLHTTP");
		} else if(window.ActiveXObject){
			//For IE 6+
			browser_request = new new ActiveXObject("Msxml2.XMLHTTP");
		}
		else{
		//Error for an old browser
			alert('Your browser is not IE 5 or higher, or Firefox or Safari or Opera');
		}
												//alert(browser_request);
		browser_request.open("GET",URL,true);
		browser_request.onreadystatechange=function()
		{
		   if(browser_request.readyState==4)
			{
			   // alert(browser_request.responseText);
				if(browser_request.responseText=="valid")
				{
					document.getElementById('logoff').style.display="";
					document.getElementById('login').style.display="none";
				}
				else
				{
					document.getElementById('login').style.display="";
					document.getElementById('logoff').style.display="none";

				}
			}
		 }  
		browser_request.send(null);
}