I don't think it will let me withdraw after it's been accepted but I'll go look.
ORIGINAL: invertmast
If you mark your offer to be sent to you as well you will get an email of your offer to the seller. Otherwise, you go to "my market" then click on "my offers" Then under the "your offer" tab marks how much you are willing to pay. It doesn't give any text you may include with your offer, as you should ask all questions you have on the item before you make an offer. That being said, if you did give questions with the offer that you would take it at XX price if 2+2=4 and no answers were given to your questions I would go and withdraw your offer and send him a message explaining why you withdrew your offer.