JQuery :: Scrolling DIV Overlap Footer On Page

I'm using this small js to scroll a div, the problem is that it goes all the way to the bottom of the page and overlapping my footer, I need it to stop before the footer. [URL]
$(function () {
var msie6 = $.browser == 'msie' && $.browser.version > 7;
if (!msie6) {
var top = $('#contact').offset().top - parseFloat($('#contact').css('margin-top').replace(/auto/, 0));
$(window).scroll(function (event) {
// what the y position of the scroll is
var y = $(this).scrollTop();
// whether that's below the form
if (y >= top) {
// if so, ad the fixed class
$('#contact').addClass('fixed');
} else {
// otherwise remove it
$('#contact').removeClass('fixed');
}});
}});