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I'm working on a page that people are telling me is working fine in Firefox 5, but not working in Firefox 4.

I'm developing on a Windows 7 box, with FF5 installed.

I followed these instructions to install FF4 in parallel with FF5: http://blog.empiregpservices.com/post.cfm/running-multiple-versions-of-firefox

And they worked fine. I created a shortcut on my (Windows 7) Taskbar, that would start FF4 with the separate profile I'd created for FF4, and all was well and good.

So I loaded up my page. It worked in FF5, and showed the same errors others had reported in FF4. So I started to try to figure out why. First thing I noticed is that I didn't have either the DOM inspector or either of the javascript debuggers installed. So I went into the FF4 addon manager, and added the DOM inspector. It ran through completion, and asked me to restart FF. When it came back up after the restart, it was FF5.

And my FF4 shortcut on the Taskbar was gone, leaving only my original FF5 shortcut.

So I went into the FF4 install directory, and ran firefox.exe from the command-line: "firefox.exe -P FireFox4 -no-remote". And the browser that came up was FF5.

Somehow, the add-on manager modified by FF4 installation to run FF5. I'm pretty sure that if I scrub the install directory, and reinstall FF4, I'll be able to get FF4 running again. But without the DOM inspector and a javascript debugger, it won't be of any use to me.

So, does anyone have any ideas about not just how to run older versions of Firefox in parallel with new versions, but how to install add-ons for the older versions? While avoiding the way FireFox is so "conveniently" updating my version for me?

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2 Answers 2

up vote 1 down vote accepted

Like it is so often, the answer is simple.

Go into the Firefox options, and turn off auto-update.

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While I can appreciate the desire to prevent automatic upgrades, it's a bad idea now. All updates to firefox have the potential to be security updates now, and given the 6 week time interval, they probably will all contain at least one security fix, possibly for a remotely exploitable hole. Since the security support model now is to upgrade as soon as it's offered or be exposed, it's a bad idea to hold back updates, even for a day or so, and exponentially worse as time goes on, since detailed information about security issues is only embargoed until shortly after the fix ships. –  Stephanie Jul 22 '11 at 1:14
    
Reasons not to use 4.0.1: MFSA 2011-28 Non-whitelisted site can trigger xpinstall MFSA 2011-27 XSS encoding hazard with inline SVG MFSA 2011-26 Multiple WebGL crashes MFSA 2011-25 Stealing of cross-domain images using WebGL textures MFSA 2011-22 Integer overflow and arbitrary code execution in Array.reduceRight() MFSA 2011-21 Memory corruption due to multipart/x-mixed-replace images MFSA 2011-20 Use-after-free vulnerability when viewing XUL document with script disabled MFSA 2011-19 Miscellaneous memory safety hazards (rv:3.0/1.9.2.18) –  Stephanie Jul 22 '11 at 1:27
    
Did you read the question at all? It's not a matter of my using FF4, it's a matter of my being able to test a website with FF4. That means installing FF4, and turning off auto-update, so that it stays FF4. I never browse the web using FF4, but so long as there are customers who use FF4, my websites have to work in it. –  Jeff Dege Jul 22 '11 at 3:24

In new versions, DOM inspector got revamped and turned into part of a fuller suite of developer tools, which now live under the Firefox menu in the web developer submenu.

Old addons can often still be run, either by toggling some version-specific preferences in about:config or (much easier) installing Addon Compatibility Reporter, which provides both an override to version compatibility checks and a feedback tool that helps both Mozilla and addon developers find out what addons are working with new versions and which are broken.

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