goodroi - 2:17 pm on Feb 26, 2011 (gmt 0)
In case you are not sure if you have been hit this algo update you may want to do a little research on your analytics.
Look at your top keywords generating traffic between Feb 1-Feb 22. Then compare it with the list of top keywords generating traffic from Feb 23-Today. This can help to identify if any of your keywords are possibly having issues.