When large websites like twitter, facebook, and instagram are created?

[Ethan]

First off, remember that every web designer gets a different start. A typical approach is to host it locally or on a dedicated webserver (if you're looking free, 000webhost might do, but its not a very, well, "professional" host). This usually involves port forwarding or something similar. Just remember that if you ever port forward, only open ports you need and watch for security issues...

Second off, any unique work is automatically protected under US copyright law (©). Many companies choose to register a trademark (®, ™) to better protect themselves. When a company starts to generate revenue, registering is a good idea, but the us copyright law should be fine for starting off.

Finally, make sure to have a good background and a good motivation. For the background, know lots of web code languages, you will be using multiple at once! (HTML, CSS, PHP, SQL, JavaScript, etc). For motivation, you need to have a good idea from the start and then take lots of time building it up!