Just like every programming language is compiled to Machine code, what is Web programming compiled down to?
Not every programming language is compiled to machine code. Most popular programming languages are
interpreted.
Kind of same for Javascript, but that's indeed a programming language. The Javascript engine shipped with your browser would interpret and execute each line, line by line, or something like that.
Most JavaScript engines make use of
bytecode to increase speed. Bytecode is almost like machine code, but it is still not run directly by the computer, instead it's more of just short-hand for interpreted code.
Aside from all that, the three languages (Programming, Markup, etc) you will want to familiarize yourself with are JavaScript, HTML and CSS. This is only for the in browser stuff. If you want to start looking into programming server side stuff (database etc) then there are a number of options. Most people start with php+mysql. I myself would recommend looking at
node.js though.
A great resource for learning web programming is
w3schools as Sorunome mentioned. If you want to look more in depth at HTML+CSS+JavaScript though, I'd recommend
Mozilla's Developer Network.