MDN HTML

MDN HTML Reference discusses what are HTML, Hypertext, Markup, tags. It also contains links to key resources such as HTML Basics article, HTML tutorials and HTML reference. Besides, there are beginner's tutorials(Introduction to HTML, Multimedia and embedding, HTML tables, HTML forms), Advanced topics(CORS enables image, CORS settings attributes, Preloading content with rel="preload"), References(HTML reference, HTML element reference, HTML attribute reference, global attributes, inline and block-level elements, guide to media types and formats, HTML content categories) and Related topics. This page could be used as a referene to HTML material. I could use this page to refresh my HTML knowledge, to learn something new or to find out a particular topic I'm dealing with.

MDN CSS

MDN CSS Reference page structure is very similar to HTML one. It briefly discusses what is CSS and its current version. It also contains key resources to CSS introduction, CSS tutorials, CSS reference. There are CSS tutorials(first steps, building blocks, styling text, layout, solving CSS problems), reference(CSS concepts), CSS cookbook used for common layout patterns, Tools for CSS development(validation, Firefox Developer tools, Web developer extension for Firefox). The MDN CSS reference is same as HTML reference and could be used to learn CSS basics, to learn advanced techniques or to discover interesting new techniques. I would use the page to find out information on CSS topics.

Summary

The trusted resource is always important when learning something new because you don't want to learn somebody's mistakes. If you are copying a code from someone on the Internet there is a low chance it is going to work because each programmer tends to do code in their own way. And it is better to learn a proper techniques in the beginning not to confuse oneself with somebody else's coding preferences. That's why it is called a trusted resource the one you can trust and it will always work.