position: fixed;
.<script type="text/javascript">
$(document).ready(function($) {
$nav = $('.fixed-div');
$nav.css('width', $nav.outerWidth());
$window = $(window);
$h = $nav.offset().top;
$window.scroll(function() {
if ($window.scrollTop() > $h) {
$nav.addClass('fixed');
} else {
$nav.removeClass('fixed');
}
});
});
</script>