function renewSession(url) {
    var xmlDoc = null ;

    process=function() { 
        if ( xmlDoc.readyState != 4 ) return ;
        window.status="Renewed session "+xmlDoc.responseText 
    }

    if (typeof window.ActiveXObject != 'undefined' ) {
        xmlDoc = new ActiveXObject("Microsoft.XMLHTTP");
        xmlDoc.onreadystatechange = process;
    }
    else {
        xmlDoc = new XMLHttpRequest();
        xmlDoc.onload = process;
    }

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

function unavailable() {
	alert('Not available now. Please come back later.'); return false;
}