Not sure about the US but there are loads of complicated laws about it in the UK.

It all boils down to whether they've taken your money or not. If they've actually charged your credit card and received the money in their account then they should ship the item to you for the agreed price. If however they've just reserved the amount and it's currently being held by the credit card company then the transaction hasn't actually been completed yet.

About false advertising they have to show that it was a mistake and that nobody would actually believe that the price was correct. A chain called Argos advertised a TV for £0.01 once. Several thousand people bought it but Argos didn't supply the TV's in the end. A few people actually tried to sue them because of that but their case was shot down because it was obvious that the price was a mistake.

Kodak advertised a £300 digital camera as a special offer for £100. Since £100 isn't too unrealistic for a digital camera and they also advertised it as a special deal they were on shakey ground. The order confirmation email was also worded poorly and implied that the order was accepted and was being processed. In the end they decided to sell everybody the camera's at £100 each as a sign of good faith.

IANAL etc...