At what point do you give up on a site which has been banned by a popular search engine? That is the topic of one thread over at WebmasterWorld. Many sites have been reported to have been banned or penalized by Yahoo! Search. The unusual thing is that the site owners honestly do not know why the site was banned. In fact, the site does well in other search engines like Google, Ask Jeeves and MSN. So now what?
Several individuals feel that leaving the old site up but excluding Yahoo!'s bots in the robot.txt file AND putting up a new site specifically for Yahoo! but excluding that site from the other bots in the robot.txt file is the solution. This way, the site continues to rank well in the other search engines and you get to start from scratch with Yahoo!.
Do ditch the old site and start from scratch with Yahoo! Search only.