When I open Firefox, I receive the following: Firefox can’t find the file at jar:file:///C:/Program Files/Mozilla Firefox/browser/omni.ja!/chrome/en-US/locale/branding/browserconfig.properties. I have seen the help that suggest I go to "about:config" and the browser.startup.homepage, which I have done. But the suggestion doesn't state what I should do once there. What do I do to the browser.startup.homepage?
Often this is just an issue of Firefox missing a file or of a Firefox-related file being damaged. It can usually be fixed by reinstalling Firefox.
Hope this helps.
The browserconfig.properties file was used in older Firefox versions to set a localized homepage.
This has been changed in Firefox 63 to have support for non-localized homepages, so seeing a reference to this file is likely a leftover from an older Firefox version.
You can check the "browser.startup.homepage" pref on the about:config page and reset this pref via the right-click context menu to the default value.