I just have a few questions about the 'Sleep' function.

1. Is the number an exact time? Or is how long it lasts judged on CPU speed?
2. Is it possible to have a variable in the brackets instead of a number? Like
Code:
Sleep(x);
?
3. (not really related to Sleep) is it possible to create a popup message that opens up over all the other windows? Like a custom error message popup?

Answers appreciated.