How to write code for your own website

Answer 1

just get started.
start bit by bit

Answer 2

start with HTML to design basic structure the add animation using CSS and functionality using javascript

Answer 3

Start with HTML. You have to know its fundamentals in order to make the websites basic structure and its very easy :)
Then move on to CSS. Its almost the same as html and its essential for designing(decorating/animations etc) the website and making it look good.
Then for full functionality(popups,confirmations etc.) learn Javascript. Its different from the other two but at the same time not hard at all. You can use this app as well as codecademy.com for learning it properly. Happy designing :)