On the Content Network, I know that the keywords don't necessarily matter - you should focus on optimizing the websites.

So what if there are websites that are sending me a couple thousand impressions and no clicks?

Can someone give me a number of impressions I should go by before blocking that traffic source or do impressions and CTR's not matter on the content network?

Also, does it not matter how many keywords I add per adgroup (within the content network) as long as they are specific to the ad?

-Zak