Rankings for keyword variations dropped over weekend?

[zealmedia]

One of our clients has seen significant decreases over the weekend for a number of keyword variations. There have been no significant site changes, no crawl errors reported and our competitors don't seem to have been affected.

The decrease has coincided with the launch of a display campaign, but surely this is just coincidental?

Any thoughts would be appreciated...

[Malarowski]

Sit tight for a few days. If it still stays bad, compare your linking profile to competitors, maybe there is something shady in there (not accusing you of anything) that Google caught outside of a major update. They adjust their algorithm about 500 times a year according to a recent video, so chances are there are daily minor changes. Could be a fluke, too. We had rankings drop down from 5/6  to 10 for a week, and promptly bounce back up again without any interference.