I know there is a solution to stop the mvc framework to process \"favicon.ico\" requests (solution), but i don\'t know why is it looking for this icon in the first place.
You better have one since it is standard to most browsers to look for the favicon.ico however if you really don't want to have it and get rid of the error just add this line in your RegisterRoutes class.
routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" });