It does take some work to get the two not to step on each other, but yes. Check out this thread: can I install versions 3 and 4 on my PC at the same time? | Firefox Support Forum | Firefox Help.

I wouldn't bother if I were you. While you can customize ff4 and make it look very close to version 3, it still has some serious flaws. I have to admit that the drastic changes to the user interface were enough to make me downgrade back to version 3.6.16. I upgraded both my work computer (standard tower configuration) and my personal laptop. I was planning on upgrading my mac-mini too but never got around to it due to the issues I had with ff4 on my laptop and work computer.

My experience with ff4 is that it is unstable and runs much slower than previous versions, despite claims to the opposite. I experienced lock-ups that forced me to manually exit ff4 via the task manager on both machines. The lock-ups occurred after the browser had been running 3-4 hours (I usually leave my browser running for long periods of time). FF3 is a resource hog. No doubt about it. Version 4 was supposed to fix that issue but I'm not seeing any improvement. It's still at the top of the list in the task manager for both CPU usage and memory consumption.

Even if none of the above were issues, I'd still have downgraded. I absolutely detest the new user interface. Hiding everyday tools from the user as the default is very micro$oftish and just a bad idea. I know you can change the settings and end up with look and feel similar to previous versions. But even so, what you're getting in the long run is the proverbial pig in lipstick.

Thanks, jscher2000. I'd love to try it, but what ocertain says in his (her?) reply makes me nervous about doing so. FF3, even if it is a "resource hog", works fine for me, so I think I'll wait for further developments which I hope will bring an easier and less fussy upgrade experience.

And thanks, ocertain, for your advice. Whereas jscher2000 seems to be a PC guy, I see you're a Mac user, so I can relate more easily to what you're saying.

Cheers!

@ ocertain I lasted about a month with the FF4 & tonight I couldn't take it any longer I went back to FF 3.6.16.. Prior to making the change back I did take some of supports suggestions to make 4 look like 3 but they were just bandages on a cut to try & stop the bleeding in the end the cut was still there..

I found that FF4 was like having IE & if I wanted to use IE I would have.. I don't know who designed FF4 but if you're going to upgrade something you have to remember the operative word is 'upgrade' so making it worse was the wrong direction..

As a former systems analyst I found FF4 a disaster in response & in visual appearance, so I wonder how many end users were in the testing group for this product & how much negative testing they did before they released it ?

They can send me an alert when the soup is cooked & ready to eat until then I will stay with FF3..

Thanks, mom2rescues. FF4 looks less and less attractive, so I guess my instincts to resist installing it were right, even though I've been getting those little "FF4 is here" windows popping up on my screen for weeks.

Take my advice & ignore the messages & I'm generally a computer geek but not this time.. Before I made the change I saved my bookmarks to a file on the desktop just in case because I have a lot of them & have them special folders & didn't want to lose them.. I changed my update function on FF from 'automatically update' to 'let me choose my updates' since I didn't want them switching me back automatically so you may want to look into doing that; just a suggestion..

I've got "ask me what I want to do" checked in Prefs, and when the most recent message came up, I clicked "no thanks", so that should stop it coming for awhile. As you say, I'll wait for a message saying the soup is cooked (and the pasta's "al dente") before taking on FF4.

I have been nervous about updating FF ever since I had trouble with updating to an earlier version a few years ago. Trying to get back to the previous version (which had worked fine) was a time-consuming task that I really didn't need, and I've been wary of updates ever since. I reckon updates should be a breeze, just like updating other software, and I get rather "exercised" about having to go looking for lost bookmarks, settings etc.

I'm a Mac guy, so I'm used to things going pretty smoothly in the software realm, but FF updates have unfortunately been a rare exception. I like how FF3 works, and I appreciate that FF4 is a laudable community effort, but still...

Initially I didn't want to do the FF4 update because I received a message that it wouldn't support some of my addons & my Norton Safe Web, but I was having bad issues with Twitter & 'they' suggested to do the upgrade to FF4 & that would absolve the Twitter issues..

hmmmm shame on them & to tell you the truth after I did the upgrade I just went onto the Norton Safe Web site & did the download again..

But I am back with FF3 & hopefully all will be well & judging from all of the complaints on this site about FF4 they should recook it because initially I thought it was just me.. This is a new pc with Windows7 Professional (another issue) which my son sent me for Xmas to replace my other laptop that had Vista & went to hard drive heaven so I thought it was my pc which would not be unlike a Microsoft product..

I did have some issues this morning which sent me to tizzy heaven but I had about 5 windows open & I was watching a video stream so I guess I was beating it up a little..

I will wait for them to hopefully do some more testing & I will check back with this site to see if people are still complaining..

The worse thing they did for themselves with FF4 was under the help tab they put a button to click on for 'complaints & compliments' (paraphrased) & you don't want me to have access to something like that.. I must have hit that button & left my words several times a day my Italian got the best of me.. Sorry for them..

Hope all goes well from this day forward for all of us because I really love & brag about FF.. **sigh**

Yeah, I really like FF3 so I hope they get their stuff together for FF4. If I could upgrade easily to FF4 and find that I could live with a few initial but eventually solvable problems, then I might be able to give them some advice for tweaks based on my experience, although such advice would be far from expert and likely not very useful. However, I'm not presently convinced that an upgrade would be something I could live with, and getting back to FF3 being a further trial, I'm just not willing at this point to take the risk. I think doing so is for those folks who are knowledgeable about how to deal with the difficulties and who are willing to do the Beta work, so to speak. I guess I'm just not a Beta-testing kind of guy.

Well I hope that they do make necessary changes to it including the actual appearance of the tool & menu bars & some other things they changed like the location of some of the necessary icons.. Also, FF4 runs slower than 3 so I hope they give that a B12 shot..

I'd be happy if FF4 looked and worked just like FF3, but with all 3's problems worked out, and with the ability to easily change its look, layout etc. That makes much more sense to me than entirely changing its look and layout as a fait accompli and then saying, you can change it back to the old look if you really want. Folks like to have choice.

Before I did the reverse change it gives you a warning message that FF3.6 may not be fully protected against virus but I have Norton Anti Virus & their Norton Safe Web Lite so I wasn't concerned & took the leap.. Its always my feeling its up to the company to satisfy the end user & the end user shouldn't be asked to jump through hoops to make all these little adjustments to make the product usable; Microsoft is famous for that.. I was disappointed as soon as I saw the results after the FF4 download & was sorry I did it.. Perhaps others like the changes & I sat with it a couple of weeks to try & get comfortable with it but just couldn't.. I'm just hoping it will be fixed.. I think you can go on Mozilla's web site & take the tour of FF4 to see what its like without doing the download..

Actually I did take a look at the video of FF4's new appearance and features, and it all looked great onscreen, but I reckoned that the reality of dealing with it all at once might not be so great.

I keep getting the pop up windows about "FF4 here" click for the download but I'm ignoring it & if I can get away without using it I will.. My son works as an IT for a firm in Washington & he does testing for other software/hardware companies so I'll check with him about any improvements on this FF4; I've already told him I made the switch back & why.. Good luck & update if you try it I'm interested in others opinions..

I've decided to take a look at the Chrome browser just in case..

I've tried Chrome and it seems to work okay, but I'm not sure if I feel entirely comfortable with Google. The company seems to be good in some ways e.g. it seems to be trying to be eco-friendly, but there are other things I hear about it that concern me.

Another thing about FF is that I like the idea of FF and Thunderbird being a pair. I think it goes way back to when Netscape was a 2-in-1. :)

Anyway, I'll let you know if I get my courage up with FF4.

I agree with you about the Google issues I don't even use their search engine because of it.. It would be sad for me to leave FF as a browser & I don't use Thunderbird as an email client I use Incredimail which unfortunately is a Microsoft product but I like the goodies that go with it that Thunderbird doesn't offer.. But I also use Wikimail as an email client..

I will wait & see with the 4.. Good luck with it & enjoy your weekend.. Enjoyed the chat..

Me too, and thanks.  :)

this just came across Twitter from FF:: " What was your favorite version of Firefox before Firefox 4? Tell us why. Be specific. "

They must be getting a lot of complaints etc so obviously I answered the Tweet a couple of times..

The problem that made me wary of updating FF started a few years ago. I'm not sure if it's really been fixed or not, and as we've discussed here, I'm reluctant to update to FF4 before it has been fixed.

It's a relatively small problem, but it's a real annoyance in my day-to-day use of FF. It has to do with the size of the "Edit this bookmark" window that opens when one clicks on "Bookmark this page" in the "Bookmarks" menu. After that first ill-fated update the window opened to such a small fraction of the size it used to open to that it was very difficult to find one's way around the bookmarks list (see the first attached).

After the usual trouble, I managed to get back to the previous FF version, but eventually I discovered an add-on called OpenBook which allows one to resize that tiny window so that it opens at a size big enough to see a large selection of the bookmarks list (see second attached and note the tiny "+" at the bottom left which allows the resizing). So I was able to update FF and get the big bookmarks window. [Why a big bookmarks window isn't a built-in feature of FF is an utter mystery to me. Isn't it a no-brainer?]

But with subsequent updates, there was a question about whether OpenBook would work with the new version of FF. Folks suggested work-arounds but it meant getting down into the software bowels, and I didn't feel too comfy with that, so I continued to be wary of updates after that. Updating to FF3.5 was a big thing for me, but I only attempted it after I found out that OpenBook itself had been updated to work with 3.6.

Now we have FF4, and initially the only way to get OpenBook to work with it was to go into the software bowels, but it seems that someone has come up with a supposedly easy solution here : http://host-db.com/tvb/archives/2011/2011-03-28.html#_3 (look at the latest post, and by the way, you can see a description of the software bowels approach below it). "OpenBook-v4.xpi" looks to be the ticket alright, but the description of how to install is in French and it seems to be for Windows, not Mac, so I'm cautious.

But even if the OpenBook problem has been solved, that still leaves all the other issues with FF4 that you've mentioned, so I'm going to stick with 3.6 for now.