europeforvisitors - 3:55 pm on Jan 30, 2008 (gmt 0)

Same here Adsense earnings have dropped by around 40%. But I guess that is normal with January.

Depends on the topic. If your topic is consumer widgets, you might hit a peak during the Christmas-shoping season and see a plunge after January 1; if it's leisure travel, you might experience a slump late in the year and a big boost in January. (The latter is my pattern and has been since the 1990s.)