Some kind of invalid click. Usually they take the clicks AND the earnings out, but not always.

Also, if you accidentally click on your own ads it will show that way.

It could be a 0.01 click in a different currency that got rounded down to 0.

Do they count clicks on CPM ads?

okay, cheers. Bit duff if the bid is that low to earn less than a penny.

Definitely wasn't me clicking on the ad, I know that's naughty and monitored so avoid it like the plague.

"Adsense Stats" are notoriously out of whack these days for many people. There are algorithms counting clicks and reporting revenue, algorithms taking clicks away and removing revenue, algorithms checking up on algorithms no doubt and algorithms still to be written which will most certainly make it even more confusing for the existing algorithms. There are probably even some algorithms sitting around drinking beer and contemplating their ones and zeros for lack of anything better to do. Used to see clicks with Zero earnings much more frequently in the past but it's not so prevalent an occurrence for me these days. I've often wondered if it's a result of a certain type of invalid click (cancelled or expired campaign ad that's showing on a cached page or some such thing) that gets caught by a particular algorithm but that algorithm only knows how to keep money out of the system. Good news is, if they take the click away, you won't lose any more revenue (at least from that action).

Used to see clicks with Zero earnings much more frequently in the past

Me too. I always assumed that it was down to people clicking on CPM ads.

It's not adsense stats going out of whack. It's CPM ads, check your performance reports.

[edited by: eek2121 at 3:37 am (utc) on Mar 3, 2014]

adsense stats*

I have many 1c clicks, 100 clicks for a dollar, this is bs.