There isn't. jwz mentions that he was unsuccessful lobbying the release of the 3.0 source.[1] For the purposes of this discussion (since you only ask about th

There isn't. jwz mentions that he was unsuccessful lobbying the release of the 3.0 source.[1] For the purposes of this discussion (since you only ask about the browser here), according to Brendan, 4 was like 3.[2] Seibel mentions there that Brendan says he tried to get it released, too. The big rewrite that everybody talks about is Gecko (under the stewardship of Gessner, I think), when 5 got ditched and the next release jumped to 6. It's still listed on the MXR homepage (under Classic). Then, ho-ho, there came another new flavor at the genesis of Firefox proper, Aviary, which is also indexed on MXR. I don't know what sets it apart from pre-Aviary besides that it ditched the old XPInstall stuff. (Yeah, XPIs still exist, but most people don't realize that's not XPInstall anymore. That's the new-ish "toolkit" install system.) 1. http://www.jwz.org/blog/2009/09/that-duct-tape-silliness/ http://www.jwz.org/blog/2009/09/that-duct-tape-silliness/ 2. http://gigamonkeys.wordpress.com/2010/03/07/two-rewrites-redux/ http://gigamonkeys.wordpress.com/2010/03/07/two-rewrites-red...