I am trying to add custom domain name at Bit.ly, I followed the instructions of Bit.ly for creating A Record and I followed Dynadot instruction too (http://www.dynadot.com/community/help/question/create-A-record?popup=1), however I am unable to verify my domain name wbmaistr.ws or probably I am trying to check it too fast, as wbmaistr.ws is already pointed to Byt.ly
I don't see anything wrong with your settings. How long after creating the 'A' record did you attempt to verify? It's possible the change had not yet propagated fully.