brizad - 7:11 pm on Aug 29, 2007 (gmt 0)
A few weeks ago I had one campaign running at an overall CTR of less than 1%. On a lark I turned off the ads from midnight to 6am and the CTR shot up to over 4%. I don't know exactly why it should happen that way but it sure did. I plan to test this concept more in the future.