$(function () {
        $(window).bind("scroll", function () {
            var sTop = $(window).scrollTop();
            var sTop = parseInt(sTop);
            if (sTop >= 50) {
                $('#nav_menu').addClass('navbar-fixed-top');
                $('#nav_menu').removeAttr("style");
                $('#menu_navbar-nav'
 
).attr("style","margin-left:130px;");
                $('#nav_bottom').replaceWith('<div id="nav_bottom_2"><br/></div>');
            }
            else {
                $('#nav_menu').removeClass('navbar-fixed-top');
                $('#nav_menu').addClass('navbar-static-top');
                $('#nav_menu'
 
).attr("style","width: 82%;margin-left: 9%");
                $('#menu_navbar-nav').removeAttr("style");
                $('#nav_bottom_2').replaceWith('<div id="nav_bottom"></div>');
            }
        });
    });