One of the reasons why so many responses here are high quality and useful is that the site has very a specific notion of content which is "allowed".

That means that users don't get annoyed by questions about HTML, PHP, or other computer things - that they may well be able to answer.

Whilst it's not a great crime to post semi-related topics once or twice. If users did it all the time then the quality of visitors, contributors and the site in general may fall.

(Or the site might still be great; just more unfocussed. Who can say ..?)