When you rollover one item of your menu, the font-size expand to 225%, the color fade to yellow and the other items are giving more space to the hovered item, when you roll out it will take its place back in the menu.
First add dependencies in your head document, you will need jQuery ui for this plugin.
In your menu, add to each item the class flashMenu.
You can customize the speed, font-size and easing, look for your document ready in the file jquery.menuZoomer.js, you may need to tweak the line-height.
fontSize : "300%",
easing : "easeOutExpo"