First of all : That is sooo sweet of you, wanting to donate to Mozilla ! Mozilla definately does accept Visa cards - could it be that there's something wrong with the credit card ? Maybe you could ask here : https://usa.visa.com/contact-us.html Also see : https://donate.mozilla.org/en-US/ and : https://donate.mozilla.org/en-US/faq#item_1 You shouldn't have to go through all this trouble, when you're trying to do something really good like this (so sorry !)