$(document).ready(function() {
    $(".toplevel > li").hover(function() {
        // Slide menu down
    $(this).children('ul').css({ visibility: "visible", display: "none" }).show();
    $(this).children('ul').children('ul').css({ visibility: "visible", display: "none" });
    }, function() {
        // Slide menu up
        $(this).children('ul').css({ visibility: "visible", display: "none" }).hide();
    });
});