My fastest win!

This is a game I won in just 13 moves due to a blunder by my opponent. I started a few games with 1a3 and it went well at my level.
http://en.lichess.org/pliKYwso/white#25

Not in this game, but in many others I try to start with 1a3 ...2c4 ....3 e3... 4d4 ...formation. Are there some serious weakness to it? I found it usually gives me relaxing middlegame with initiatives.

Not familiar with the opening.
No offense intended, but just about any opening works when your opponent makes serious blunders.

There doesn't appear to be any serious weaknesses to the Andersson or the way you are opening. At your level, focusing on the center, development, not hanging pieces, and taking advantage of your opponent's blunders should be the focus.

IMHO.

Of course opening knowledge will become more and more imperative in the future, the deeper you go.