Может быть этот код?
/*---------- MEGA CATEGORY MENU ----------*/
$(".mega-post-categories-latest-posts div").hide();
$(".mega-post-categories-list ul li a:first").attr("id","current");
$(".mega-post-categories-latest-posts div:first").fadeIn();
$('.mega-post-categories-list ul li a').on('mouseenter', function(e) {
e.preventDefault();
$(".mega-post-categories-latest-posts div").hide();
$(".mega-post-categories-list ul li a").attr("id","");
$(this).parent().attr("id","current");
$('.' + $(this).attr('title')).fadeIn(100);
});