Please consider turning on send info to Mozilla before posting a question. This helps us help you.

I do not know, what did you do..... ? Did you get a update, install software ?

https://support.mozilla.org/en-US/kb/how-to-set-the-home-page Leave that Tab open and go to the page you want as your home page and then click Use Current Page.

Check to see if you have malware : https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware Use more than 1. Save all reports, Google each line before deletion or ask for help https://forums.malwarebytes.com/topic/9573-im-infected-what-do-i-do-now/

Please let us know if this solved your issue or if need further assistance.

I did not do an update or install software. My computer was on and I clicked on the Firefox icon to get to my home page and I got the Apache2Ubuntu Default Page instead. When I click on my home page icon or enter the https for my home page, only this notice from ubuntu appears. I might try setting a different page as my home page and see if that will hold. But I'm worried that I have been infected and don't want to make it worse.

That is why I gave the information above for you to scan with Malware Scanners.