To contribute Firefox information, visit one of the "full" pages
(browser-support-html, browser-support-css, browser-support-dom, or
browser-support-ecmascript) and click on one of the Y/I/N values to
enter an editing mode. You can make changes and then submit them for
approval. What this basically does is send me an e-mail with the
change requests, which I'll look over and then make any appropriate
changes to the table information.