As was said before you can learn HTML to make the sketch of the page, CSS for the design of the webpage and JavaScript so the users can interact. The difficulty depends on how fast can you learn or how good you are at solving problems.
If you want to make it online you can use online hosting services or buy yourself a server (and I think you can use your computer as a server, but it need to be always turned on) to host the web. Also you need to have a domain so users can access the page.