chicagohh - 3:20 pm on Jul 9, 2010 (gmt 0) [edited by: chicagohh at 3:24 pm (utc) on Jul 9, 2010]
I did add a site-wide navigation bar that did not exist before.
On your 2000 page site you just added 40,000 links to your internal link profile. That's a significant change from just upgrading the CSS and could cause your site to drop. Hopefully, it will come back, but you made a major change to the internal link structure.
[edited by: chicagohh at 3:24 pm (utc) on Jul 9, 2010]