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Adsense drops by 95%. Crawler errors.

Ive been on Xenforo (import from vBulletin) for about two years. About 6 weeks ago my Adsense income, clicks, active views and ad sessions dropped by 95% overnight. They all dropped to near zero. I don't believe I changed anything about the site.
Adsense reports crawler errors of "page not found" for;


Those pages lead to a Xenforo error of "page not found"

Can anyone offer any insight to my problem?
Thanks for the replies. I don't think the crawler errors are the cause of my significant drop in Adsense revenue. Google made changes on 18th December which affected many sites. Here's a 400+ post thread discussing the issue in the Adsense support forum.

A quote from that thread....

"As part of Google’s efforts to increase brand safety for advertisers, Google is making changes to the way it buys impressions on URLs that are uncrawled. More specifically, starting on December 15th, AdWords and DoubleClick Bid Manager will adopt more restrictive bidding on ad requests coming from URLs that are uncrawled. This is necessary to avoid the risk of ads running on sensitive content."

The website Search Engine Roundtable has three articles discussing the issue

SER January 6

SER January 15

SER January 16


Well-known member
I’ve been noticing this.

On brand new threads the ads won’t load as they haven’t been crawled yet. Pretty quickly after the first impression they start displaying though.


XenForo moderator
Staff member
Quality is being valued over Newness and Quantity
Another forum down rank by Google.
Only if you arent producing quality content :) The drivel and instant gratification content has moved to the likes of FB and Twitter. Forums are moving to fill the gap of high quality content and troubleshooting which those sites who really promote quality forum discussions are doing very well.