It's weird, it always happens only at the first tab load.
Quite harmless bug, anyway.
I have FF19.

ANNOUNCEMENT:
Version 2.3.1 has been released with the following features:
* Attempted to blindly fix a non-reproducible checkbox-duplicating bug in the new "My Tags Checkboxes" feature under Firefox 19.0 (current version is 30.0) [reported by phaolo]

I downloaded FF19 but was still unable to reproduce the bug.
I then thought of a theoretical scenario that might cause this kind of behaviour and attempted to fix it blindly.
Please reload your engine page, make sure it reads version 2.3.1, and let me know if it solved the bug.

You didn't really have to work so much for that! :O
Anyway.. it seems blindly fixed! Thanks! (2.31 ok)

Also, lol that bugfix description XD
Newer FF versions just require too much memory for my old pc, aren't compatible with some useful addons, or limited the layout customization too much.

That's OK. I enjoy debugging.

I respect you choice.
I continued to use MS-DOS until 2005, refusing to move to Windows for more than 10 years.
However, do be aware that your browser security is probably limited and your PC is more vulnerable, because many changes across the versions have to do with plugging security holes (or so they say...).

ANNOUNCEMENT:
Version 2.3.2 has been released with the following features:
* Added behind-the-scenes support for game ID change (Divinity: Original Sin is the first (and hopefully the last) game to have its ID change since MaGog launched)

ANNOUNCEMENT:
Version 2.3.3 has been released with the following features:
* Added mean and total file size statistics at the bottom of the File Size column on the results page
Note: In case you were wondering, the entire GOG library currently consumes 855 GB, bonuses excluded.

ANNOUNCEMENT:
Version 2.3.4 has been released with the following features:
* Added Inuktitut to the list of searchable languages (amazingly now supported by Ittle Dew)

Thank you! I care about these things.
Fixed. With your permission, I will make this a silent fix, i.e. without log or version number change.
Need to conserve these version numbers...

Absolutely! Glad to help - I know that's the sort of thing that drives me batty. :)

Uh, I've never used the MyDate tag so far, but now it shows random integers everywhere (-3, 82, etc)

Sorry about that. Was experimenting with some stuff and had a "glitch". Should be gone now.
However, if you clicked on (i.e. edited) any of the "My Date" or "My Stars" while the bug was in effect, these were saved and you will have to delete them manually.
Sorry.

Ah ok, but you don't need to be sorry for anything, you're doing a great job and I'm just reporting some bugs : )

Thank you. But it was such a clumsy bug that I had introduced. Have to be more careful when playing around with the live database...

ANNOUNCEMENT:
Version 2.3.5 has been released with the following features:
* Fixed a short-lived but embarassing bug that caused "random" values to appear "spontaneously" in "My Date" and "My Stars" fields [reported by phaolo]