While I was editing an answer that I had deleted, it displayed with lines and a Math processing error
Here's a screenshot:
This affected all the other answers to the same question and the question itself.
The strange thing is that it has occurred, as far as I've seen, with this page only.
What may have happen?
The browser was Firefox 13.0 on Windows 7.
Added. Also the same problem with IE 9.
Added 2. I deleted all the text of my answer and wrote "Deleted to test a bug. Deleted to test a bug. Deleted to test a bug." and ... the malfunction disappeared.