The original headline of this post was "New Firefox upgrade left Tab Mix Plus behind, so I downgraded," and that story is below. Since then, a reader, in comments, offers a link to a beta, a "dev-build," a work in progress of Tab Mix Plus that works with Firefox 3.5. Now I'm back up with FF 3.5, and Tab Mix Plus again works for me, all my settings intact.

It's a beta, so I might later upgrade to the final release, but this is fine for now.

Upgrading Tab Mix Plus was a snap, much easier than downgrading to yesterday's Firefox. Firefox Setup 3.5.exe, still in my download directory, and it overwrote the older version. My first act was to go that TMP link above. Clicking on the Dev-Build link there kicked off the install.

Thanks to Smokie for the link. If you're still running FF 3.2 or less, don't go here. Download the version at Mozilla Add Ons. (If you don't know what Firefox version you're running, pull down Help--> About Mozilla Firefox and read the version number off the screen.)

I had actually seen that TPM forum post Smokie links to, but I blew past it. I'll explain how/why in comments.

Last night, 10:11 p.m.
I upgraded to Firefox 3.5 today, forgetting that essential extension Tab Mix Plus lagged well behind the last Firefox upgrade.

When the new version installed and came up, Tab Mix Plus was not compatible with it, and was gone. I stumbled around the Web without my tools, overwriting tabs, unable even to close the last tab in a window and start fresh. FF 3.5 might be faster, but I wasn't.

I had forgotten how much of my delight in Firefox actually comes from Gary Reyes' nimble extension -- being able to move and duplicate and open a gazillion tabs, unclose and retrieve Web pages from a list and generally browse, blog and code my way:

Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager. -- Mozilla Add Ons

I could wait for the other wonders of Firefox 3.5. I don't need a "porn mode" to hide my history, and I didn't think my old version was slow. But Browsing without Tab Mix Plus was cramping my style.

So I went to Old Apps and downloaded Firefox 3.0.11. (Old Version has it too; these sites are great for simple free versions such as classic ws-ftp.)

I uninstalled Firefox 3.5 through Control Panel's "Add or Remove Programs" link, opting to leave my settings there for the old version to find.

Re-installing the old version hit a snag. The install kept asking me to reboot, which I did, twice. Something had to have been left behind.

Using the file manager, I went into Program Files--> Mozilla Firefox and saw a Firefox.exe which shouldn't still be there and couldn't be opened, and an uninstall helper.exe which did nothing. I killed them both, and this time the browser installed, picking up all my bookmarks, settings and extensions, including Tab Mix Plus.

I can now happily have 137 tabs open again.

I'm going to wait for Gary Reyes to make a version compatible with Firefox 3.5 before I budge again. (He has. I budged. See the update above.) If you haven't upgraded to FF 3.5 yet, go get Tab Mix Plus and set it up for the way you want to browse.