Can I ask question related to HTML, JavaScript, CSS, etc., here? If not what is right community of Stack Exchange to ask? Stack Overflow? And if I have question about WordPress, would be I post question to http://wordpress.stackexchange.com or http://stackoverflow.com? or both?


Without a more concrete example of the kind of question you'd like to ask, the answer to your question here is: It depends.

Most likely Stack Overflow would be the appropriate choice. They have tons of questions tagged html, css, and javascript. But that's no guarantee your question(s) would be on-topic there. Read the Help Center.

As for WordPress Development vs. Stack Overflow, that also depends. There is likely to be a bit of overlap in each of the sites. Read the Help Center. If it's still not clear to you, you can always ask on the respective Meta site or in chat (with enough reputation to do so).

If nothing else, take the Tour and read the Help Center so you get a better sense of what is, and especially what isn't, on-topic for the site.

One thing for sure: Web programming questions are off-topic here on Web Applications.