When they beat on everything and it drops you have to wonder if people thought it would beat by even more. In this case I would guess that investors thought that the 2013 outlook would be even better. Must be people expecting to be completly blown away but were underwhelmed and chose to take some profits... pretty lame
I think it's just a case of buy in anticipation, and sell on the news. Also, some traders may have been disappointed with the 2013 outlook, but Generac has always given very conservative guidance, and has consistently exceeded it. In the conference call Q & A, they admitted that the current quarter, just like last year, is going full tilt, with backlogs at 7 weeks. Ignore the knee jerk reaction, and hold.