How do I stop all minimized tabs from maximizing when I start a new webpage?

Do you have that problem when running in the Firefox SafeMode?
http://support.mozilla.com/en-US/kb/Safe+Mode
Don't select anything right now, just use "Continue in SafeMode."

If not, see this:
http://support.mozilla.com/en-US/kb/troubleshooting+extensions+and+theme...

Problem is gone when starting in SafeMode.

Then you need to troubleshoot your extensions to discover which one is causing that problem.

Don't know what you mean . . . what are extensions?

Please read the 2nd support article that I hyperlinked in my first response.

All fixed . . . it was an extension that had to be updated. Thank you so much . . . Emily