Header Buttons to change catagory list

[CaptainInsano]

Hey guys

I found a interesting oscommerce site that has a great idea on it, i have tried to find out how they did it but im not sure.

There simply links on the header banner that switch your whole catagory list to a different list and you can change it between 3 lists.

the site is http://www.amainhobbies.com/ if anyone has any idea on how they did it. Please help me

Cheers, Captain Insano!