Keep Session Alive

[Ramchandar]

In my aspx page i want the lot of informations to be filled by the user. But wen the user takes some break to fill the form n resumes after some time the page gets expired. So to keep the session alive i used the following javascript code but it didnt work.

function KeepMeAlive()
    {
        var myImg;
        myImg =document.getElementById('keepAliveIMG');         
        if (myImg)
            myImg.src = myImg.src.replace(/\?.*$/, '?' + Math.random());
    }
 window.setInterval("KeepMeAlive()", 2000);

So it would be helpfull if any one suggests some idea for calling the server method asychronously using javascript by which i can make the session alive.

Thanks in advance.
Ram