The Hacker News site design is simple and unintrusive. Sometimes, it is a bit too subtle and I don't notice the end of the comments page. I hit the down arrow, try to put the focus back on the document, act confused and then notice that I have reached the bottom of the page.

This is easily fixed with a site-specific user stylesheet in FireFox:

1. Go to your FireFox profile directory. (see finding the FireFox profile folder )
2. Copy this user stylesheet into the chrome directory. If that file already exists, copy the content of the user stylesheet and add it to your file.
3. Restart FireFox.

The end of the page now has a small orange line that clearly signals the end of page.