It surprises me that the official FAQ for SO - http://stackoverflow.com/faq - does not contain guidelines on how to answer questions. Stuff like: "An answer should be complete, accurate, clear, ...".
I'm asking because I stumbled upon this question - HTML type string parsing question! - in which one of the answers is off-topic. The answerer based it on his guess, and he thinks it's OK to post incomplete, inaccurate and unclear answers as long as the answerer thinks that the answer might help the OP (somehow).
Such a practice should obviously be avoided, but I am unable to find an official statement that points that out.
Feature request: I'd like to see guidelines on how to answer a question on the SO FAQ page.