Multiple areas in a map.

I read some where that I will need to do something special if i have multiple areas in my map such as 2 sky boxed areas on top of each other.
Can some one give me more detail?

What do you mean?
Also, for mapping questions visit http://facepunch.com/forumdisplay.php?f=38

Say I have 2 areas in my map that have a sky box around them.

What’s the problem?

Why don’t you just try it instead of blindly following something you “read somewhere”?