Hi all! I am a huge fan of Justin York's WikiTree X applet. It is called a Chrome Extension and I used it everyday on Chrome.
Due to concerns about the information Google collects on its users, I had to delete Chrome and I lost my WikiTree X button!
The good news is I now use Opera and the WikiTree X extension works the same way in Opera.
To load the WikiTree X Chrome extension for use in Opera, you need to install this little program in Opera https://addons.opera.com/en/extensions/details/install-chrome-extensions/ and then follow the 1, 2, 3 instructions to load the WikiTree X extension. Works great and just the same as in Chrome!
I understand you may be able to use it Firefox too, but I haven't tried that.