Floating fixed columns

Need script to do the following:
(all script MUST be in external file)

Think of a "slider" or "chained select" menu. No dropdown boxes.

Column 1, 2 and 3 will only be about 100px wide.
Each will be floated left.

Column 1
HOME
Item 1
Item 2
item 3
Item 3


Column 2
Shows HOME on startup. Disappears and is replaced by the following depending on which item is chosen:
Item 1.1
Item 1.2
Item 1.3

Column 3 may show something on startup but in a general idea.
Item 1.1.1
Item 1.1.2
Item 1.1.3

Column 4 will then be displayed showing the final results.

Like the tabbed content scripts but with the tab content to the right of the tab rather than below it.