about:home is an internal page.

Let’s do a full clean re-install;

Download Firefox For All languages And Systems {web link}

Save the file. Then Close Firefox.

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Look for, and remove any Mozilla or Firefox program folders. Do not remove the Mozilla Thunderbird folder if there is one.

Do Not remove the profiles folder.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

about:home is the builtin default home page, but this page will be removed in future Firefox versions.

What Firefox version are you using?

• Help -> About Firefox
• https://support.mozilla.org/en-US/kb/Finding+your+Firefox+version

You can see all available about: pages on the about:about page.

Hopefully the reinstall will fix it.

But even if Firefox can't find your home page, you should still be able to browse using other features, such as:

• type a website address or search into the address bar
• use a bookmark to access a site you've bookmarked

You also can reset your home page if the address is not working. See this article: How to set the home page.