Firefox increasing rate since Firefox 1.0 was released on November 9, 2004, and Firefox had already been downloaded over one billion times. This number does not include downloads using software updates or those from third-party websites. They do not represent a user count, as one download may be installed on many machines, one person may download the software multiple times, or the software may be obtained from a third-party. In July 2010, IBM asked all employees (about 400,000) to use Firefox as their default browser. Firefox was the second-most used web browser until November 2011, when Google Chrome surpassed it. According
Quirks mode Web Consortium, which maintains the XHTML specification, suggests that authors of XHTML documents could consider omitting the XML declaration. Henri Sivonen compiled a list of various document types and how they are treated in the most common browsers, showing whether pages are rendered in Quirks, Standards, or Almost standards mode. The criterion used for "Almost standards mode" is non-standard table cell height rendering. This table applies to content served with the Content-Type text/html. Content served with the Content-Type application/xhtml+xml is rendered in Standards mode in Chrome, Firefox, Internet Explorer 9, Safari, and Opera. Internet Explorer 6, 7, and 8 do