I was recently implementing a Ruby on Rails method that creates flash messages with the beautiful Twitter Bootstrap styled alert message. I did however notice that although the flash messages looked almost correct, the "close" link on the right hand side was no longer correctly styled.
There are no images in the Twitter Bootstrap, so this icon must only be the English letter "x", or so I assumed.
After looking at the CSS comparison from the examples to my code and finding no help, I eventually noticed a slight difference in the "x" character I was using. It turns out that the Twitter Bootstrap is designed to use the HTML entity "×" (times symbol) instead of the keyboard letter "x".
Hopefully this can help out anyone else facing a similar confusing issue.