Personal anecdote: I was booking a room with Delta Hotels recently, and it declined my card repeated saying that my expiry date was wrong (it wasn't).<p>At some point I figured that my booking date was <i>after</i> the expiry date, which makes some sense that they would not accept it. Clearly they had the code logic to check for this, but they couldn't get the error message to tell me this?<p>Instead they threw me the old "your expiry date is invalid!" message.
A good tip to improve around the margins, but fixing your main product/service needs to come first before you devote time to details like this. This tip will increase your revenue 5% once; an improved product might increase it 5% per month.<p>In other words: prioritize.
All I saw initially was the red input box. I initially skipped completely over the error message, thinking it was an ad. Only after being thoroughly confused for a minute did I notice it.