This forum has maintained a couple of style sheets. At this time I've actually approved the removal of the vBulletin 4 default style sheet. This will leave the standard site styles on the forum.
The reason for dropping this style is that only a limited number of people are actually using it (less than .0042%), and we simply can't justify maintaining it for so few people. Our time is better focused on doing other things within the forums.
My apologizes for the roughly dozen people this impacts. Hopefully you'll understand.