When does this page open: when starting Firefox, at a certain time each day, when updating Firefox, new tab, new window, randomly?

Please post a list of your extensions. You can extract that as follows:

Help > Troubleshooting Information > "Copy text to clipboard" button

When pasting, you can remove the lower part of the information starting from Important Modified Settings.

Thanks. I opened the question here because https://support.mozilla.org/en-US/questions/976987?esab=a&s=weeklyjobadvice.blogspot.com&r=0&as=s was marked solved and I figured that it wouldn't get much notice.

However, the replies on that thread did give me something to look for. I found "Test Your memory! 1.2 true memory@lipo-technologies.com" in my FF profile and removed it.

To the extent that one data point is proof; it seems to have solved the problem. I posted the new info on that thread and would delete this one entirely but that doesn't seem possible. So . . . I've included my apparent solution and links to the other thread to tie them together in case someone finds one and not the other.

I'm going to lock this thread as PeterWolfe2012 is discussing this in another thread - https://support.mozilla.org/en-US/questions/976987