You will need to install a user script manager extension to install this script.
4chanX's thread watcher is pretty sweet. Probably one of the best features it has. But one thing it has always been seriously lacking in my opinion: The pages my threads are currently on.
More often than not, I refresh the watcher to see that my favorite thread has fallen off the board because someone forgot to bump. Not anymore! Now it's easy to see which threads need to be bumped, especially since Page 10 threads have red page numbers.