Gradual width increase on hover

I want to add a hover effect to one of my navigations for an upcoming template but I don't know how to make this bar expand in HTML instead of flash.

The effect is:

1.) mouse hovers over navigation
2.) A blue bar appears and widens underneath the nav. link to about 113 pixels


As I said it needs to be HTML (javascript is fine), I don't need the countless ways to do this in Flash.

Javascript, I would never use flash. Flash has its purpose, which doesn't include layout elements or the layout itself.

Check out http://script.aculo.us/ it's basically a library of sweet java script effects, you should be able to use that to do what you want.