From MozillaZine Knowledge Base
Using an extension
It is possible to change the wording using an extension such as Firesomething or Titlebar tweaks (both by momokatte).
- Go to your Firefox application folder. Then, go to a folder that's called "chrome". Copy that folder somewhere else for a backup.
- Within the "chrome" folder, there is a JAR file called "en-US.jar". Extract it (We assume you use US English Firefox). You need to have some software that can extract JARs and repackage them. Examples are WinRAR, 7-Zip, Winzip, etc. Alternatively, under Windows XP, you can rename it to "en-US.zip", use the built-in unzipper, make your changes, and change it back to "en-US.jar" when you're done.
- In the file that you extracted, there is a "locale" folder.
- Firefox 1.0: Navigate to locale\en-US\global.
- Later Firefox versions: Navigate to locale\branding.
- Open "brand.dtd" file.
There, you should see something like this:
<!ENTITY brandShortName "Firefox"> <!ENTITY brandFullName "Mozilla Firefox"> <!ENTITY vendorShortName "Mozilla"> <!ENTITY releaseURL "http://www.mozilla.org/products/firefox/releases/1.0.html">
You may edit that to something like this:
<!ENTITY brandShortName "Browser++"> <!ENTITY brandFullName "My Firefox"> <!ENTITY vendorShortName "Mozilla"> <!ENTITY releaseURL "http://www.mozilla.org/products/firefox/releases/1.0.html">
Then, repackage everything back exactly how it was and open up Firefox. If Firefox has issues, just restore the backup copy and try again.