I have asked some questions on stackoverflow.com and programmers.stackexchange.com and they closed and down-voted due to off topic.
Now how can I consider that which is the best network site to ask my question?
Each site has a FAQ link(example: Stack Overflow FAQ) - click on the FAQ link & review the FAQ page which will have what the on & off topic questions.
In general, most Stack Exchange sites will have these questions closed almost immediately as offtopic:
Additionally, you might want to review per-site Meta to get a feel of what's allowed or not.
Finally, visit the Stack Exchange directory to view a list of all available sites so you can judge for yourself the best Stack site for your question.
Stack Overflow is for questions that have to do with the coding part of programming. Taken from its FAQ, Stack Overflow covers questions about:
Programmers, on the other hand, is for "conceptual questions on software development". Again, taken from its FAQ, it covers:
Edit: I initially misunderstood your question, so hopefully this edit helps.
Some questions are considered off-topic or not constructive, and will be closed because the question type doesn't work well with the Stack Exchange engine. This includes subjective questions, and questions that ask for list responses. Taken from the FAQ:
Looking at your questions, I don't think that they fit well on any stack exchange site. If you want to know what is wrong with them, check out the close reasons, for instance:
These aren't being closed for being off-topic, they are being closed because they simply don't fit the Stack Exchange question format.
In other words, it's not an issue of finding the right site to ask them, it's an issue of re-writing them so they are good questions that can be answered.
Consider spending some time reviewing How to ask a smart question