[javan]

Quoting from the official Player's Handbook:
(Granted not the wisest thing to do... [img]tongue.gif[/img] )

Page 30

Challange Rating. The higher this number, the more powerful the enemy. Commonly four characters of a certain level are able to defeat one creature with a CR equal to the average level of the characters with a moderate amount of difficulty.

Monster Challange Rating.....Catagory.........Colour....Explanation
+5 and greater levels..........Impossible........Purple....Death is guaranteed
+3,+4 levels......................Overpowering....Red... ....You'll have difficulty defeating this creature
+1,+2 levels......................Very difficult.....Orange...Survival is not guaranteed, without drawing
.................................................. ..........................on potions or other magical aids
Same level as the...............Challanging......Yellow.....You can defeat a couple of these before resting
character or less
-2, -3 levels......................Moderate.........Blue. ......You'll take a few wounds
-4, -5 levels......................Easy...............Gre en.....Worth lettle XP but won't hurt you much
-6 and less levels...............Effortless..........White.... .Not worth your time

I think that this scale was drawn up for the Original Campaign for pre-epic characters. A level 8 monster may be impossible for a level 3 character to defeat but the gap between 38 and 33 is not as significant.