There will be a system Maintenance Tomorrow for Adsense.
Tomorrow, our engineers will be performing routine system maintenance
from 10am to 12pm PDT. Although you won’t be able to log in to your
account for 2 hours, we’ll continue to serve ads to your pages and
track your earnings as usual.For our international readers, we’ve
converted the maintenance start time for a few cities around the
world:Toronto — 1pm Saturday London — 6pm Saturday Cairo — 8pm
Saturday Mumbai — 10:30pm Saturday Melbourne — 3am Sunday Thanks for
your patience, and enjoy your weekend!Posted by Arlene Lee – AdSense
Source Inside adsense
I just hope that this will not affect our earnings
Updates : March 01,2009, Adsense is ussually doing updates to make the system works better. I can say that during Adsense Downtime there are some Minimal affect on my earnings. You can see my Adsense Updates at our Adsense Category Rest assured tha this blog will give you updates on how to earn more from Adsense.