Accroding to Uncle Cecil, in Is “different than” bad grammar?:
Woohoo… I’ve been proved wrong by a Cecil column. Now is my cue to exit from this thread in utter disgrace, and reject all slang usage unless it’s directly endorsed by Cecil Adams.
The above was not seriously meant, by the way. I don’t think I’ll do THAT.
F_X
From the link given above:
This has me puzzled … As a Brit I have never heard another Brit use the phrase “different than” - it’s always “different to”, which is presumably where the Aussies got it from?
As soon as I started to communicate with Americans on the internet I noticed they were saying “different than”, and it has always sounded odd to me!
Julie
Presumably that’s where the Aussies got it from… I have G online right now, and he says he’s never noticed.
F_X
This Aussie has never heard “different than”. It’s “different from” usually, except when it’s "different to. In fact, come t’ think of it, I say “different to”.
Never heard it, eh? Well, I guess that kinda resolves that question. 
F_X