No, that's not right. The currently available Firefox 5 is not a beta version.

I read that during Firefox 5 testing, the McAfee add-on caused a lot of crashes or other problems, so it's very unfortunate that they aren't going to update it.

You could try out other similar add-ons, such as WOT (I haven't tried it myself: Web of Trust - Safe Browsing Tool :: Add-ons for Firefox).

so is there anynews as to when firefox may have a compatible version to site advisor?

No one but McAfee has the code for that add-on, so there's nothing anyone but McAfee can do to make it compatible. If you rely on this add-on, stick with Firefox 3.6.18.

Security suites usually update in the Fall (e.g., "back to school" time frame), so you can hope for an update around then.

how can I get the old verson of firefox back? I had 4.? something b ut i upgraded found out I couldn't use site advisor so I unistalled firefox and now can't find an older version to download

Due to security vulnerabilities, rolling back to Firefox 4.0.1 is not recommended. Firefox 3.6.18 would be the safer choice.

Here's the process to roll back:

First, I recommend backing up your Firefox settings in case something goes wrong. See Backing up your information. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, download and save Firefox 3.6 to your desktop for future installation. http://www.mozilla.com/firefox/all-older

Close Firefox 5.

You could install Firefox 3.6 over it (many have reported success) or you could uninstall Firefox first. If you uninstall, do not remove your personal data and settings, just the program.

Unless you have installed an incompatible add-on, Firefox 3.6 should pick up where you left off. If there are serious issues, please post back with details.