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;
}

function logOutUser( userId ) {
	var xmlHttp = getXmlHttpObject();
	
	var url = "logout.php";
//	alert( url );

	xmlHttp.open( "POST", url, true );
	xmlHttp.send( null );
}