Firefox does not have a built-in feature to "roll back" to a previous version. Also, the difference between Firefox 27 and Firefox 26 is not noticeable, so I'm not sure what version you would want to reinstall in place of Firefox 27.

One thing you might check is the Troubleshooting Information page. Either:

• Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

Click the Show Update History button in the first table to see what previous updates were installed.

I guess I should caution that messing around with your wife's computer could cause more problems than it solves, so you probably want to admit to the oops and get approval before making further changes...

P.S. Now that you're registered, you can help edit the Knowledge Base to make it clearer. Please feel free to help.

Your current level 29 is TERRIBLE on my iMac and I want to go back a level, until you fix it!!!! Help?????!!!!!

Hi williansnod, could you take 5 minutes to try this: How to make the new Firefox look like the old Firefox. For security reasons, if that allow you to get the interface to a comfortable state, you'll end up in a better place.

Thanks, but I decided I don't want this, how do I uninstall it? Thanks in advance!!!

I found it, not to bother!!!!

Well, you have the link for future reference.

Mozilla.org maintains a publicly accessible archive of all past versions of Firefox. The link to it is located in the middle of the following page:

https://support.mozilla.org/en-US/kb/install-older-version-of-firefox

There is also a quick link to version 28.0 for US English.