Foundation own menu is jumping

I created a menu with special buttons.

You can find it here

  1. The problem I have, when you make a mouseover to one of the buttons (the little Pics under the Main menu), the other ones jump down.

It doesn’t happen with other standard themes of RW, so there must be something in Foundation that makes it.

  1. I like to show the active button in another color, so you can see which Text you see right now. What is the correct order therefor?

.menu-item a:active {content: url(’%resource(My Picture)%’;}

How can I solve my two problems?