A Webmaster Blog
Few Days Back there was a fight between Mattcutts and Jeremy about copying there designs and user interface.
Initially Jeremy pointed that Google has copied their template for promoting IE7 promo.
You can check out those two promos pages where yahoo and Google posted IE 7 Promo page.
Mattcutts gave response immediately about this issue saying apologies for copying. He said when they were launching there ad words results they made a long research and created a friendly user interface for ad words like light green background color with thick border.

Yahoo has changed its ad words display as similar to Google like light background color with thick border.

Again Google has removed the background color and thick border and separated the organic result and sponsored results with a thin border. They have kept a light background color for the ads, which are placed on the top of the results and also at the bottom. Yahoo followed the same procedure copying.

Yahoo has also followed Google in displaying the no of characters in displaying AD. Initially Yahoo use to allow 190 characters in a body but now it is restricted to 70 characters in a block where as Google gives two lines of each 35 characters.

Yahoo was Successful in Copying.