Does Adsense allow competing programs such as Contextweb in the same page?
My second question is if I have 2 ads unit.
Is it right that the first ad in the first unite will be the highest paying ad. The first ad in the second unite will be worse in terms of revenues and that the last ad in the second unite will be the worse?
Your answers will be greatly appreciated. Where can I read more about these?
You can't mix and match these services on the same page.
Have you read ContextWeb's TOS?
If you don't meet monthly minimums in terms of dollars or impression you FORFEIT what you earned, it doesn't roll over, and they only pay 50% (less than Google) and hold back 5% for "bad debt" so you absorb their cost of doing business.
They look interesting, pay faster, but I wouldn't touch them with a 10 foot pole as long as their TOS remains as it is as they can absorb that 5% for bad debts out of their share, not mine.