Page views v Ad impression

What constitutes an Ad impression

[John]

I think this should be fairy straight forward ;-)

If I have three Google Adsense blocks on a page does Google count this as 1 Page Impression or 3? Anyone know for sure?
Thanks

[novice]

If I have three Google Adsense blocks on a page does Google count this as 1 Page Impression or 3? Anyone know for sure?

It will count as 1 page impression regardless of the number of ad units.

[google.com...]