Sudden, harsh drop in adsense CPC

[realmaverick]

Good afternoon guys.

I recently made some changes on my website; added "noindex, follow" to the meta robots tag on a gallery, for all pages >1.

From that point, my adsense dropped daily and continued to drop until my income was literally cut in half. I've left it, as I figured it would work itself out, but it's not. At present I'll lose thousands per month unless I can figure out why this has happened.

Adsense isn't displayed on any of the effected pages. But the effected gallery pages, link to the download page, where the adsense ad is located.

One theory, is that the referring gallery pages, now have a lower quality score due to the fact they're no longer indexed. And perhaps the quality of the referrer has an impact on the value of the click?

The CTR is stable, but the CPC is what's had the dramatic drop.

Any suggestions?

Thanks

[netmeg]

(EPC)

Are you seeing the same advertisers?

The first thing I'd probably do is go into the new UI and run some reports, to see if your drop is across the board on all pages, all ad types, all ad sizes, etc.

[realmaverick]

I only run 1 ad, on the entire site of 300x250. I don't have ads on the rest of the site as it's gallery based, very high impressions with low CTR.

[netmeg]

Is your ad enabled for both text and image? Are they both down? Are you seeing the same advertisers? How long was the EPC stable before the drop?

Sounds like smart pricing, or some of your advertisers might have pulled out. I really don't see how those other changes would have made a difference in EPC.

[realmaverick]

[tinypic.com...]

This is a graph of adsense

[realmaverick]

I reversed the change and I kid you not, the very next morning my adsense ecpm was +50% and today a further +50% and back to normal. This is after a couple of weeks of terrible earnings, that occurred the very next morning after the noindex tag was added.

So for whatever reason, noindexing the gallery pages had an adverse effect on the proceeding page containing adsense.

IMO the connection is related to the quality of the referrer and because the referrer wasn't indexed, the CPC dropped.

It sounds odd but there's no way this was coincidence.

[leadegroot]

Could still be a coincidence - to better establish the cause, you need to (give it a bit and then) repeat the noindex, see if the epc falls agin then take it off again and see if it comes back again.
Then you have something worth reporting! :)

[realmaverick]

Of course, doing that would give this more merit. But I didn't post for merit, I just wanted help resolving my issue and posting my results.