It was the most common weekday, July 17th. I needed to test the display of the site in different browsers, for which I launched Firefox 3 installed on my site (I also have Firefox 2.0.0.11 on my computer, also for debugging purposes). Lys immediately issued a message that a new version appeared - 3.0.1 and strongly suggested upgrading to it. I click "update", a connection is established, 2 megabytes of updates are downloaded. Firefox is being updated. Then, as usual - after the restart, it checks the compatibility of the add-ons, found only an incompatible Pencil, updated it. Finally, the familiar Fx treshka window opens with the title of the window
“Firefox successfully updated” . But what do I see? The Mozilla page opens, in which in large letters it says "
You are now using Firefox 2.0.0.11 "! Do I have to say that there was no limit to my surprise? I climb into the "
Help " -> "
About Mozilla Firefox " and indeed, I have Firefox 2.0.0.11 with the interface from Firefox 3.0!

')
I try to run installed Firefox 2.0.0.11. As usual - check compatibility of add-ons, launch Firefox and ... throws me almost to the same page with the words "
You have successfully updated to the latest version of Firefox ". I also climb into "
Help " -> "
About " - shows version 2.0.0.11.

I immediately climbed on Habra, hoping to see a topic about this problem, but in the topics I found about updating Firefox to 3.0.1, not a word about such a "joke". The same is in the comments.
Axis - Windows Vista Home Premium SP1.
Installed add-ons in 2.0.0.11 - only Pencil 1.0.2, in Fx 3 - HTML Validator 0.8.5.2, Pencil 1.0.2, Web Developer 1.1.6.
UPD: guilty found thanks to
Auren . Guilty was the toolbar Megaupload.
UPD2: caezar showed me where I really should watch the Fx version, thanks to this I noticed that it turns out that Fx 2.0.0.11 was updated to 2.0.0.12. You can also notice this in the second screenshot.