To a certain extent, Wikipedia is your friend:

http://en.wikipedia.org/wiki/White_tie

...interesting that Highland Dress is mentioned in this article, eh?

I recently attended a black tie event where the definition of "black tie" was r-e-a-l-l-y being stretched by a lot of the men. The attitude seemed to be "I have enough money that you certainly can't expect to tell me how to dress...I'll wear what I want and if you don't like it you can just try to make an issue out of it". If I were a cynic I'd say that this was a very good way to tell "new money" from "old money"...

Best

AA