$(function() {
    var $sidebar = $('.banner');
    $window = $(window);
    offset = $sidebar.offset();
    topPadding = 0;

    $window.scroll(function() {
        if ($window.scrollTop() > offset.top) {
            $sidebar.css({
                'top': '0',
                'position': 'fixed'
            });
        } else {
            $sidebar.css({
                'top': '',
                'position': ''
            });
        }
    });            
});