Is your Windows 8.1 a home version, Pro version, or Enterprise version? I think the problem might be occurring with all 3, actually.

Based on the "new profile test" it appears to be caused by a setting or other profile-specific data/file/add-on, but I don't think we have tracked down which one it is.

I'm not sure about that last point: "FF starts on its own." What does that mean? Often this can indicate malware on your system that is sending a URL to your default browser, either based on a system event or on a timer.

Do you want to try the new profile test? Since it takes quite a bit of work to move your data and add-ons to the new profile, you might decide it isn't worth pursuing, but here's how you would get started if you want to try it.

To test how Firefox runs "uncustomized" on your system, could you do a two-minute experiment?

Create a new Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder.

Exit Firefox and start up in the Profile Manager using Start > Run (home screen with the small icons, or Window key+R):

firefox.exe -P

Don't delete anything here. Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, choose a name like Aug19, and skip the option to change the folder location. Then start Firefox in the new profile you created.

If you set your preferred home page, exit Firefox and start up again, are all of those problems with your regular profile solved?

When returning to the Profile Manager, you might be tempted to use the Delete Profile button. But... it's a bit too easy to accidentally delete your "real" profile, so I recommend resisting the temptation. If you do want to clean up later, I suggest making a backup of all your profiles first in case something were to go wrong.

If you want to move data to your new profile, this article is a good place to start: Recover important data from an old profile.

Rather than say yes or no to this being helpful I will say "possibly". I do, however, very much appreciate your efforts. Frankly right now I just don't have the time to pursue this, especially considering how much I have already put into solving this problem.

As per spontaneous start-up, I shut down everything except the cpu itself. In the morning the blank tab page is looking at me when I turn on the monitor.

Again, thanks.

Okay, if Firefox opens by itself, that can indicate a malware infection that launches a URL in your default browser. As a test, you could make IE your default browser for a couple days and see whether you start getting an IE tab open in the morning.

For future reference: Troubleshoot Firefox issues caused by malware.

Thanks, jscher. Made IE my default browser and there it was looking at me in the AM. This does not happen during the day and I have never been on the computer when either set default browser has opened.

So I think there are two elements to this:

(1) Remove any unwanted software (2) Clean up any scheduled tasks

To start, I suggest opening the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install. Take out as much trash as possible here.

Next, you could try several malware scanners. Our support article lists tools other Firefox users have found helpful: Troubleshoot Firefox issues caused by malware. Note: those are free and take a while to run. If they terminate quickly and prompt you to buy, your computer has a serious infection.

To check the Windows Task Scheduler:

• Windows XP: Start button > [All] Programs > Accessories> System Tools > Scheduled Tasks

• Windows Vista/7: Start button > Control Panel > System and Security > Administrative Tools > Task Scheduler

• Windows 8: ?? You might try the charms bar search box if you don't find it in the control panel.

Some past threads on the "dsite" problem:

• How can I keep Firefox from opening a window to website tofushopnews.com
• How do I get rid of sponsorship tabs that open automatically?