Where can I see what kind of questions are or are not relevant on /programmers?
From usability point of view, it's pretty hard to find.
The Help Center has all the information that you need. Specifically, check out these pages:
If you aren't sure if your question is on-topic or if you need help to narrow down the scope or make other improvements, you can always ask here on Meta or in the chat room, The Whiteboard.