special credit card

please excuse my ignorance but i am about to ask a question i am sure has been answered on here before, but after searching for 15 minutes i couldn't seem to find the answer.

what is the special credit card that people say exist where you can go to your bank and ask them for one that you can deposit, lets say 5 dollars into, so that you can submit the card over the internet to be sure that the company doesnt charge you more money that they say they will?

i'm heading to the bank shortly and i can't remember what to ask for.

thanks,
greg

Visa gift card, maybe? Try searching for that on google and see if that's what you're talking about. )

just use this http//www.webcertificate.com

its on the front page smartypants