Can I ask questions about non-default Drupal core modules or themes, on Drupal Answers?
Yes, you can.
Questions can be about any Drupal module and theme, both the Drupal core one, and the third-party ones you find on drupal.org; it could be also a question for a custom module you created. If you are asking about a third-party module (or theme) that you find on drupal.org, I would suggest to report a link to the project page.
Keep in mind that you could be asked to show the code you are referring on the question; if you are not willing to show the code, the answers you get would be too generic to be useful.
Yes, you can ask such questions on Drupal Answers.
i can't guess the 30 characters answer :) but thank you for your replay.– joneMay 6, 2011 at 13:20
@jone: That wasn't meant for you, your question was fine. It is simply only possible write an answer with at least 30 characters, so I had to put something in it. kiamlaluno did a better job and actually put useful information in it, so he got my upvote :). Also remember to accept the answer you like.– BerdirMay 8, 2011 at 23:27