Board Thread:Support Requests - Getting Technical/@comment-188432-20130406153509/@comment-4674838-20130407165136

w3schools is a good site for quickly looking up basic information. It has very high SEO and quickly pops up in search results, making it easy to find. But if you're looking for more in depth info, I would recommend https://developer.mozilla.org.

In this case, their border-radius page may have some useful information, it says that percentage values were implemented in a non-standard way prior to Firefox 4, and that elliptical borders were not implemented until Firefox 3.5.

If I were to take a wild guess, it's possible that this user's browser is pre 3.5, and doesn't support 2 radii. Maybe it interprets border-radius: 50%/5%; as border-radius: 50%; since it can't support an ellipse. That would be one possible explanation for the screenshot.