slideUp/Down() does not look good on all computers

I have noticed that the slideUp and slideDown animations are jerky and delayed on many computers, especially if you are using Firefox with extensions or a computer with low (<1GB) RAM. Experimentally, I have replaced these with show and hide animations, which look slightly different (changing opacity and width along with height), and noticed that the animation is a lot smoother for some reason, without losing quality on fast computers.

The cosmetic disadvantage is that the width changes, which for text boxes like sub-menus means that the link texts get linebreaks while sliding, which does not look good. Changing overflow is no solution, because we want linebreaks on longer menu items.

I will try to learn more about jQuery to see if we can find a smoother solution here.