does fog speed up or slow down gameplay in unity web player

this is pretty self explanatory. I can not wait to test it coz my game is very, VERY laggy. Im using unity web player for my game.
Thanks!
Sh.If.T
2014-15

It slows it down.

From Unity - Manual: Graphics performance fundamentals :

"Simple Checklist to make Your Game Faster:

  • Do not use fog when it is not necessary.
  • …"

(you might want to read the other bullet points on that list too).