Do you recall where you added it?

• If you added it to your desktop shortcut, you can edit the "Target" of the shortcut.
• If you added it to your home page setting, then you can edit that but it's a little tricky without launching Firefox. Here are some thoughts:

Try to directly open the Options page as follows:

Type or paste the following in the Windows 7 Start menu search box (or Run dialog), and press Enter to execute it:

firefox.exe -url "about:preferences"

That should launch a single Firefox window with the Options page displayed.

If Firefox does a crash recovery, however, it might open other pages. If that makes it impossible to edit your home page setting, you can bypass crash recovery by renaming some files/folders:

After terminating Firefox, open your currently active profile folder as follows:

Type or paste the following in the Windows 7 Start menu search box (or Run dialog) and press Enter to launch Windows Explorer in this folder:

%APPDATA%\Mozilla\Firefox\Profiles

In that folder, do you see a semi-randomly-named folder? If so, click into it. If you find multiple such folders, find the one that was most recently updated.

Look for a file named sessionstore.js which is created during a normal shutdown. If you find that file, rename it to sessionstore.old.

Note: By default, Windows hides the .js extension. To ensure that you rename the file effectively, you can turn off that feature. This article has the steps: http://windows.microsoft.com/en-us/windows/show-hide-file-name-extensions

Next, find the sessionstore-backups folder. Right-click > Rename the folder to sessionstore-backups-old so that Firefox can't find it at startup, but you still have the files for future reference if needed.

Then try launching directly to the Options page and editing your home page setting.

Success? If not, we'll move on to a file edit approach.

And you might need this as well: The most common reason for Firefox to go crazy launching tabs is if you tell Firefox instead of using an external application display it yourself. More info and a workaround in this article: Firefox repeatedly opens empty tabs or windows after you click on a link.

sparkmanpl said

Firefox 49.0.2 Windows 7 Professional I have added a URL to my options to be opened at startup. Since then when I open Firefox it repeatedly opens "New Tabs" until I cancel firefox. How do I remove the URL from my startup list? Or How do I start tell Firefox to ignore the startup list when I start it so I can remove the URL?