The Mozilla Developer Network
One of the most important sources of information on front-end web technologies is the Mozilla Developer Network or MDN for short. The MDN webdocs include references and tutorials for the core technologies HTML, CSS and JavaScript.
Essentially, if it’s not on MDN, then it doesn’t exist.
MDN also includes details of upcoming technologies that will land in browsers in the future or are available as experimental features.
Wherever possible, we will add links to the MDN pages for things we use. However, if we forget to link, or if you are searching for something we don’t cover, then simply add “MDN” to your search engine query and you should find what you need.
For example, try searching for “MDN grid” and you should find the MDN grid layout page.
Did you search for it? This is a good habit to form now. Also, if you keep searching for MDN pages then you will train your search engine to find the pages you want.
MDN is vast and comprehensive, including content for all levels of experience. It’s usually worth checking the first few search results as one may be exactly what you are looking for.
So be careful. For example, your search might also pick up the documentation for the grid property. This page is talking about a shorthand property and will assume you already know about grid layouts.