var startTime=new Date();
        var responseTime = 'nulo';
       
        function overlay() {
            elem = document.getElementById("overlay");
            elem.style.visibility="hidden";
            elem = document.getElementById("bodydiv");
            elem.style.visibility="visible";
        }
       
        function time() {
            endTime=new Date();
            responseTime =(endTime.getTime()-startTime.getTime())/1000;
            document.getElementById('<%= lblTiempo.ClientID %>').outerText = "Tiempo en cargar: " +responseTime +" segundos.";
        }