What controls tab highlighting in vB5?
 

I seem to have ended up with an odd situation whereby both the /online page and one of my custom pages, make the "Blog" tab highlight.

I have no idea what controls the tab highlighting in vB5, does anybody know where I might go to have a play with this and see if I can sort it?

(It's not a style issue since a new style still shows the problem, but the official demo doesn't, so something's gone wrong somewhere).