How i can make a website like facebook or twitter?

Great idea! First, you have to purchase web hosting. Go for an established and reliable web host such as the ones recommended on http://buywebspacetoday.com/recommended-web-hosts/ and sign up for a shared hosting (regular hosting) plan, as it's the most affordable type of hosting and has all the features you need for a typical website. Once you get your hosting, go to your control panel and look for Fantastico. Use this tool for a one-click install of Wordpress, a content management system that will allow you to create pages, write posts, add links, edit the design, and basically do a lot of stuff to create an awesome website. Good luck! Good Luck!

and where do we start?