Hello - I'm new to the forum, happy to be here!

Please forgive if this is in the wrong forum section - I did my best to get in the right one. I'm open to constructive criticism.

My issue: I have a project in mind which I think will be fairly easy considering my willingness to learn and the simplicity of it in theory.

Basically, I want to make a site A with a bunch of empty question boxes. I'd like the input into these boxes on A to be posted the corresponding boxes that exist on site B then post to the B site with the info input from A.

So, for example, site B asks a new user for desired user name, pass, security question.
Site A would mirror site B. The user of site B would answer the q's on site B then hit submit. I want this hitting of the Submit button to perform the same action it would on B's site.

This is the simplest way I've thought of to describe what I'm looking for - pls let me know if I need to clarify.

My main question is, what language would be most helpful in producing this site A? Html? XML? CSS? Java? JavaScript?

Thank you in advance for all helpful responses,
Rob