Support for Firefox 3.6 may will end when Firefox 10 is released on January 31, 2012 or Firefox 11 on March 13, 2012. So how did Mozilla arrive at this time frame? Well, it is 12-weeks from the initial release of the Firefox ESR on November 8th (8.0) or December 20th (9.0). Now, you are asking what is Firefox ESR? Firefox Extended Support Release is as of now, more of proposal. The purpose of Firefox ESR is to address issues that have come up for certain groups such as small & medium business, enterprise, academic, and government with the current rapid release process (more about this here). Bottom line, Firefox 3.6 support is going to end sometime in the first quarter of 2012 which would be almost one year from the Firefox 4 release back on March 22, 2011.