That's right. The almighty F-word was breaking how some stylesheets were loading for deviants who were accessing the site from computers with overly sensitive system-wide profanity filters installed. These users' browsers likely stopped parsing the stylesheet entirely upon reaching the word in the stylesheet, leading to a fairly ugly and/or broken page.

This article points out two things:

  1. It's hard to test for end user computers because you never know when something they have installed is going to mess up your site.
  2. It's important to be professional ALL the time not just on things the end users are going to see.

http://dt.deviantart.com/journal/We-Give-a-F-How-the-Site-Loads-392679726

via CSS-Tricks