According to a post on ThreadWatch (via Search Engine Lowdown) an email invitation from Google offers selected AdWords beta testers the opportunity to use up to 200 characters in the description field - up from the current limit of 70 characters - in a bid to improve click-through. The poster surmises that the move may presage "a concerted attack" on Yahoo's advertiser base - "After all, the extra chars were (IMO) one of Ys strongest differentiators from the AdWords product."

And a quote from the Google email: "We will alternate showing your regular ad text with the longer version of the text. We plan to experiment with slight layout variations of the longer ad text in order to determine which layout design will perform the best."