How about deleting the icon and making a new one.

Might check Tools -> Settings -> Home section and make sure the Homepage and new windows option isn't using some funky URL. Might just try and set it to Blank Page and see what happens.

This is what Firefox will first attempt to load when you start it.

Here's a screenshot of what Mark is referring to.

You can check the target line in the Firefox desktop shortcut (right-click: Properties) to make sure nothing is appended after the path to the Firefox program.

• https://support.mozilla.org/en-US/kb/wrong-home-page-opens-when-i-start-firefox-how-fix

Try to start Firefox in Troubleshoot Mode to see if that works.

• Windows: hold down the Shift key while starting Firefox
• Mac: hold down the Options key while starting Firefox

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode

Mark both issues as resolved and have a nice day.

https://support.mozilla.org/en-US/questions/1438547