How to grow block menu on hover I am trying to make secondary menu grow on mouse hover. just like this site

we can see on the bottom of the page. menu block can grow bigger and show more menu. 

any idea what technique used to make something like that. or maybe a module or maybe jQuery. right now i'm still googling but still got no clues.
Please let me know some idea about this.

Regards

mbahlol
pardon for my english
Here is a jsfiddle that will show 3 different techniques. http://jsfiddle.net/3rYCs/