How do I make a site like facebook?

Start learning basic html and css. once you are good at that try working with Javascript to make your sites more interactive. From there you can start learning PHP and MySQL to help you create the meat of your program. Its not that hard, i've have built like 15 different social networks for fun, if your dedicated you could have a good looking site done by the end of the summer :-), just try to learn stuff in the order I said above cause itll make the most sense...