What web design language should I learn?

Learning a "web design language" to build a single site is like learning Latin to translate a single document. It's not the best use of your time.

But if you really want to learn how to make a website, you'll want to start with HTML then CSS. After that you'll want to learn how to install a CMS (Wordpress or something) and skin it. Unless you're building a unique web application, there's absolutely no need to try to learn PHP or a similar backend language as that will take months/years with minimal return.