This trick only works with your own auctions. But here is a silly bug or maybe it is working as intended, who knows.
Go into your auction house, and with it open tab into windows and change your date to 2 or 3 days previous, tab back into Diablo 3, and you may have to change tabs (to say Sell back to Auctions) to get it to show up, but the cancel button will be there.
You have to have the auction window open to have this work.
Sunday 10 June 2012
How to Cancel Auction house Items in Diablo 3
Sunday, June 10, 2012
sQren