Notice missing impressions and clicks in your Adsense stats today?

On doing my regular checks of my Adsense stats I only noticed only a tenth of the traffic and clicks I would expect to see for this time of day.

I was not alone, its wasn't a drop in visitors, but scheduled maintenance of the Googles Adsense reporting system which is delaying reporting.

As with previous maintenance you can properly expect the correct stats to be seen after midnight PST

Here is what Google’s blog has to say on the matter:

"Slower stats

You may notice more of a delay in your AdSense and Google Ad Manager stats than usual today, as our engineers will be performing some maintenance work on our system. Please be assured that ads will continue to be served to your pages, and all activity will continue to be tracked as usual. Although it may take longer than usual to see impressions, clicks, and earnings reported in your account, you'll be credited for all valid activity on your sites. We apologize for the short notice, and appreciate your patience as we work to keep our systems updated for you. " 

http://adsense.blogspot.com/2009/03/updates-on-account-access-and-reporting.html