java script Count Down Timer in asp.net 3.5

//After you login, put the time (i.e. in minutes from database) in to a hidden feild from server side.

var sessionTimeout = "2";   // Put the value of that hidden feild in to this variable
var globalmins = 1; // Substract one minutes from the hidden feild and put it in to this variable
var timeOnPageLoad = new Date();

var redirectToWelcomePageTimer = null;

//To redirect to the welcome page
var redirectToWelcomePageTimer = setTimeout('RedirectToWelcomePage()', parseInt(sessionTimeout, 10) * 60 * 1000);

var milisec = 0
var seconds = 60
var minutes = globalmins;


function display() {
    if (minutes + ":" + seconds == "0.1") {
    }
    else {
        if (milisec <= 0) {
            milisec = 10
            seconds -= 1
        }
        if (seconds <= 0) {
            milisec = 0
            seconds = 60
            minutes -= 1
        }
        if (minutes <= -1) {
            milisec = 0
            seconds = 0
        }
        else
            milisec -= 1
    }
    var timestring = "Your session will expire in " + minutes + ":" + seconds + " Minutes"
    $('#showtimeleft').html(timestring);
    setTimeout("display();", 100)
}
display();

//Session timeout
function RedirectToWelcomePage() {
    window.alert("Session expired. You will be redirected to some page");
    window.location = "Default.aspx";
}