<p>I'm trying to process a credit card transaction in .net and it works perfectly in Safari, Opera, and IE. When I try the same transaction in Firefox it sends two requests and I end up with a double charged card. From a quick search on Google it seems that this is an issue with Firebug but I am unable to find a way to stop this double post. </p>

<p>Does anyone have any idea on how to prevent Firefox (and Firebug) from doing this?</p>

Use a
nonce
, a unique key which is only used once.
Send a unique number along with the form fields to the browser (this is often done with a hidden input field), and store a copy on the server with the transaction. Within the form, change the number on submit.  Validate that the keys match when processing your requests.
There may also be a clear explanation of what's happening on the front end, and that issue could be eliminated client-side.  It's best to solve the double-submit problem on the server, simply because there are so many ways in which a double submit could occur.