A while back Google allowed AdSense advertisers the
ability to set up what they called channels. This let you track
AdSense clickthroughs and the like to specific pages.

Cool feature – Trouble was you had to go back to each of those pages
and insert some new code. Not the end of the world but still a fair amount
a work.

Now Google has set-up URL specific tracking that can be managed right
from your AdSense account page without inserting any new code. I set-up
about 20 pages in 2 minutes. Very nice!