Every month I have a small amount taken from my AdSense payments for "Invalid Traffic".
(I actually just discovered this by taking a look at my "payments" page -- which seems to be the only place this is mentioned. AdSense does not provide alerts or warnings re invalid Traffic)
I have yet to find a solid explanation for what exactly this means.
Some have said that the issue is "Facebook traffic" or "Twitter traffic".
I don't even have a Facebook account, so I have a hard time understanding how I could be directly responsible for any illicit traffic coming from Facebook.
As for Twitter, I do tweet links to content as I assume everyone does.
The amount deducted every month tends to equal about 1 day's earnings -- or about 3.3%
I am certainly not doing any black-hat or illicit link building. And the traffic to the site seems healthy and normal.
Any ideas for how to address this problem and get back that 3% loss?