Who can explain these stats?

I was just checking my stats and noticed something very strange. The number of visits suddenly dropped as of Sep. 1st and  got back to their normal value on Sep. 13th as you can see in the attached screen shot.

I didn't think too much of it at first, but I now noticed the exact same thing on over 50 websites (my own and sites I'm hosting for clients) all these sites are hosted on the same server on a reseller hosting account. Since I didn't notice any slowdown or downtime of the server and I didn't hear anything like that from my hosting clients, my best bet is that the whole server got some sort of penalty by Google, maybe because of some spam sites hosted on the server.

What do you think of this?

Nico, ask you're provider maybe there was something with the server logs (corrupt file) or just a timeout while parsing the logs for awstats.

do you use a second stats program? compare both.

I think a google penalty is not only for two weeks :)

Looks like you're right. I have Google analytics running on a few of the sites and the reports show the normal traffic.

Then it is for sure a problem of the hosting provider.

For instance they may added some log cleaner and run it before the awstats update or something like that.

Have you tried to ask them about it?

no, but I will!

The traffic comes from the search engines mostly, right ?  Are you sure you did not loose your serp positions for those two weeks and then you just got them back ?

Google does not show a drop in traffic for those two weeks ? if not, probably your server stats are wrong ...

he sure the problem was an error in his logs, when he checked Google Analytics he noticed the traffic hadn't dropped. Given every one of his sites suffered the problem it was the only logical answer :)