To downgrade to Firefox 3.6 first uninstall Firefox 4, but do not select the option to "Remove my Firefox personal data". If you select that option it will delete your bookmarks, passwords and other user data.

You can then install the latest version of Firefox 3.6 available from http://www.mozilla.com/en-US/firefox/all-older.html - it will automatically use your current bookmarks, passwords etc.

To avoid possible problems with downgrading, I recommend going to your profile folder and deleting the following files if they exist - extensions.cache, extensions.rdf, extensions.ini, extensions.sqlite and localstore.rdf. Deleting these files will force Firefox to rebuild the list of installed extensions, checking their compatibility, and reset toolbar customizations.

For details of how to find your profile folder see https://support.mozilla.com/kb/Profiles

What problems are you having with Firefox 4?

Thank you Tony. I guess I am just to old and to impatient to learn new things. I don't know why but tabs bugs the crap out of me. Hope they give 4.0 the ability to disable tabs.

Tony, I don't even like Firefox four in the first 30 minutes. My gmail tab is gone, I don't have the top row of the tool bar that is in the very brief tutorial, the orange rectangular Firefox drop-down in the left corner doesn't give me anything I want to see, and the HOME icon only gives me a Google search bar and nothing more. HOME should be more than google search. Instead of the the expected tabs on my former 3.6., I can only google search? Please give me suggestions. If i choose to follow your directions to go revert to 3.6 will I have my gamil back? I need to do my gmail right now! This 4.0 has screwed up my day agenda, but you are wise.

Firefox 4 is super fast, love every thing about it EXCEPT two things: 1. Extensions/add ons are not ready and don't work ... will reinstall 4 when they get caught up 2. back button no longer displays last 5 or so addresses so you cannot skip the unnecessary "Firefox must resend the information" popup and confirmation click to go back to a previous page

I love FF4 but my school uses Blackboard and this was not on their list of supported browsers, so I have to downgrade in order to log into there.

Thanks Tony. Whoever created the piece of CR*P known as 4 should be fired like the guy who did the upgrades for Microsoft. Way to go, I would go to another browser in an instant if I couldn't go back to the others. It is moronic the changes that came through.

An alternative is to download Firefox portable (which hasn't advanced [or should that be regressed] to v.4 yet anyway). You can run it off any hard drive, portable drive, usb stick, etc. Just use it until Mozilla sort out the mess with v.4.

I don't like it one little bit either. Since upgrading to 4.0, my Xmarks keeps asking for my PIN every 10 seconds. It's extremely annoying. Also, I don't think 4.0 is very user friendly at all. I much prefer the old version and am going to revert back. What were you guys thinking????

Since loading FF4 I can no longer access my Calendar within Hotmail. I am going to reload FF 3.6 as suggested by TonyE

Hint! I didn't just install and run the file, I saved the download so even if firefox improves the improvement till it really sucks, I will still have the means to install3.6.

Thank you Tony! :) I am back to my good Firefox with pop-ups blocked or accepted from the sites on my list. I never could figure that one out on Firefox 4. Also I did as you advised in My Profile but I could not delete extensions.sqlite. Thus far I have had no negative results not deleting that file.

THANK YOU!!

I need simultaneous language translation- and this doesn't work with Firefox 4. Worse, an online shop that allowed me to make purchases using the previous FF, said that Firefox 4 is not compatible with their website!

I worked my way around the tooolbar thing but honestly, even after a month, it still doesn't feel natural or flowing. I still cannot believe that there is no clear cache button for the toolbar- it seems so simple!

Firefox 4 seems to 'Not Respond' when Twitter is updating. This gets on the nerves, believe me.

FF4.0= Fail. Sorry :-(

Excellent instructions. I didn't delete any files, but everything seems to work fine anyhow. I suspect most users of Firefox 4 installed the program assuming it was an incremental change and would not be a recognizable difference. That was the case with me, anyhow, and I regret making the change. Thanks to you, though, I have been able to delete it, and re-install good ol' reliable 3.6...thanks a lot.

@ csarff

I did the retrograde back to FF 3.6 after two weeks hated 4.0.. Also to your question about the google search I just read an article from a pc site that said everytime anyone with a FF browser does a google search google perks mozilla with $$$$ so that should answer the 'why can I only google search' question.. I personally prefer Ask.com

I went back to 3.6 also after a week or so of 4.0. Had to order something online and didn't know if I had a secure connection. Had to order using netscape 7.2 which I still use more than any other browser. Good old faithful. Why does an upgrade mean changing everything and moving everything to a different place?

@TonyE Those instructions were 100%, thanks for that. I had finally did the upgrade that FF notifications had been pestering me about for a month or two now. I was under the impression that i was downloading FF4, but instead i see that they have already done a FULL version upgrade to FF5 - which is not exactly a "home run" to say the least.

I'm a web developer and i use the FF product for debugging, design, development, and everything else, as do nearly 100% of my colleagues. If 4.0 has been considered "bad" here in the support forum, i can only describe 5.0 as disappointing. It is unfortunate that FireFox has set the standard for many years and has become the sole business tool for web development - a pressure far greater than that felt by IE (used by 0% of developers).

FireFox 3.6 is perfect. I completely understand the inclusion of new features in software development, but this addition can almost never come at the expense of performance. Similar to chrome spinner hubcaps on a supercharged sports car will cause problems down the road, features and additions need to BENEFIT the overall system.

FF5 (with the same add ons as my 3.6.18 - Firebug, Yslow, SEO Quake): - is without a doubt, significantly (and visually perceivably) slower than 3.6, as i'm sure the dev team is aware. It was most likely assumed that the users wouldn't notice the reduction in performance. we did. - the ui looks almost like a clone of chrome, with a little Safari mixed in. Chrome is actually faster than FF3.6 - meaning it blows FF5.0 away. - Chrome now supports Yslow and SEOquake, 2 highly used development tools.. If they create a firebug replacement for chrome (may already be available??) i feel that you will loose the makority of your hold in the professionals market with your newest version. - HTML in a unordered list floated left to be used as a navigation bar has odd margining - assumed CSS rendering error - IE9 is faster and renders HTML more accurately than FF5 =^O wholy S#!T i never thought that would happen

Suggestions:

PLEASE REMOVE THE BLOATING PROCESSES to regain the acceptable speed levels of 3.6 - even better, try to match the speed of chrome.

PATCH and SLOW YOUR ROLL - if you can patch 5.0 for the time being, you may be able to repair in a well executed, performance tested FF V.6

To close: I LOVE FIREFOX and use it every single day... but i won't be moving passed V3.6.18 until these issues are resolved.