How to remain bottom the scroll bar using javascript/jquery?

[Exequiel]

My problem here is that the scroll bar is not staying in bottom, after loading the data using ajax the scroll bar still on top. but when i place the code for positioning the scroll bar at the bottom before doing the function see_message_tor eply(deskid); it works, but after doing this function its not working. . can any body help me my problem?:)

 
function save_reply(theuser, deskid)
{
    var reply = $("textarea[name=reply_fields]").val();
 
    if(reply!="")
    {
        //when i put it here it works!
 
        if(reply.length >= 10)
        {
 
            $.ajax({
                type:'post',
                url:URL+"index.php/company/save_reply",
                data:{
                    theuser:theuser,
                    deskid:deskid,
                    message_reply:reply
                },
                success: function(replyz)
                {
                    if(replyz == 1)
                    {
                        see_message_toreply(deskid);
                        $("textarea[name=reply_fields]").val('');
 
                        var div = $('#main_scrol_reply');
                        div.delay(5000).scrollTop( div.get(0).scrollHeight );//scroll to bottom not work after loading the data, this is my problem
                    }
                }
            });
        }
        else
        {
            $('#pop_msg').fadeOut('fast').html("Reply too short.").removeAttr("class").attr('class','errormsg').fadeIn('fast').delay(5000).fadeOut('fast').draggable({revert: false,containment: 'body',handle:'#pop_msg'});    
        }
    }
}