Please check this link; https://www.mozilla.org/en-US/firefox/42.0/system-requirements/

Fred,

Thanks for the reply. The link tells me the requirements for 42.0, but I think I need the requirements for the 43 series since that's the one I can't get on my new laptop. I'm also having trouble finding the Firefox "systems requirements" page for various versions, although I have found it easily enough in the past.

Start Firefox in Safe Mode to check if one of the extensions (Firefox menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Try to download the full version and trash the currently installed version to do a clean install of the current Firefox release.

Download a new copy of the Firefox application and save the disk image file to the desktop

• Firefox 42.0: https://www.mozilla.org/en-US/firefox/all/

• Trash the current Firefox application (open the Applications folder in the Finder and drag the Firefox application to the Trash) to do a clean (re)install
• Install the new version that you have downloaded
• https://support.mozilla.org/kb/Installing+Firefox+on+Mac

Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you uninstall and (re)install or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

For now, don't worry about 43. Just get 42 on line.

Firefox 43 is currently a Beta version, which is on a different 'channel' than Firefox 42 Release is on. Firefox updates within the 'channel' it was originally installed on. Release to Release, Beta to Beta, etc.

OK, I followed the suggestions above, and I'm happy. As to the Private Browsing option, apparently it's only available when Custom History settings are enabled, and I wasn't aware of this.

My remaining question would be what benefits, if any might be gained by going to the beta 43 versions. Should I repost this as a new question?

Thanks to everyone.

"Use custom settings for history" allows to see the current history and cookie settings, so you can inspect and see them. Selecting the custom settings doesn't make any changes to history and cookie settings. Firefox will show "Use custom settings for history" as an indication that at least one of the history and cookie settings is not the default to make you aware that changes were made. If all History settings are default then the custom settings are hidden and you see "Firefox will: (Never) Remember History". "Never Remember History" means that Private Browsing is active and "Always use private browsing mode" gets a checkmark. "Use custom settings for history" stays selected as long as one of the History or Cookie settings is not the default to make you aware that changes from the default setting have been made.