HTML AND PHP

This time i am doing both html and php, before starting this course i had the knowledge of html only and i love to make a website. But in this course i find that html is not enough for design we must know css for decoration of html code. Aan we also need to learn about php for creating any website in which we take data from user like ymail, gmail, facebook, etc. and we also must know about any database like SQL, i which we can store that data which come from the user. And use that data for users query like when a user create an accout on any website gmail or yahoo, he gives his/her detail that time store his/her data in on server and when he login in that time we check his database that is this user is exist or not. i like this php stuff very much and i m thinking to do my final project some thing related to php.