Using http://www.alloscomp.com/bitcoin/calculator.php :

On my computer (netbook running Chrome in Ubuntu), bitp.it clocks at 2.2khash/sec. Using this, I'll give 2000hash/sec/user as a conservative estimate.

If you had 1M daily visits, averaging about 1 minute of interaction (high, but assuming you have long-form content), you'd have 12000Mhash/day, or about 2.77Mhash/sec.

Plugging this in with current rates, this ends up being $0.08/day. For 1M views. This is about 3 orders of magnitude lower than just AdWords.