Question

$("li.category-top >ul").hide();

    $(".category-top").mouseover(function(){
        $(this).children("ul").show();
    });
   $(".category-top").mouseleave(function(){
        $(this).children("ul").hide();
    });

Answer 1

Perhaps this:

$("li.category-top >ul").hide();
$('.category-top').hover(function() {
    $(this).children('ul').toggle();
});

Demo of the technique: http://jsfiddle.net/ambiguous/aKvkb/

References:

• hover
• toggle