CSS Library: Horizontal CSS Menus: Here
Animated horizontal tabs
Author: Dynamic Drive
These sliding doors based blue tinted tabs "jump up" when selected, such as when the mouse rolls over each one. This is accomplished using a combination of relative positioning and padding on each tab. The selected tab is first stretched vertically by giving it a thick bottom padding, then plucked out thanks to the CSS "top" property value that's smaller than the normal tabs'. The result are tabs that animate without any scripting.
BTW, the amount the selected tab jump up can be easily adjusted- refer to the comments inside the CSS.
The two images used: