MDN HTML
HTML: HyperText Markup Language outlines key resources and information explaining what HTML is and how to use it. This page contains a basic list of HTML elements, an explanation of how to write HTML using tags, and links to tutorials, learning areas, advanced topics, and references including full lists of elements and attributes and guides on other categories of HTML topics. These resources are very helpful when needing to refresh myself on how certain elements and attributes work, and when I am seeking information for topics I don't know much about yet. The pages on tables, forms, and using HTML to solve common problems are especially useful as well.
MDN CSS
CSS: Cascading Style Sheets contains information explaining how CSS is used to describe how elements should be rendered, information on W3C specifications for CSS, and links to tutorials on how to use CSS; references to CSS properties, selectors, values, and other topics; and to other tools and resources, such as the CSS cookbook, which contains basic layout patterns that can be used as a starting point for design inspiration and to learn new layout techniques and how they work. These resources are valuable for learning and relearning design functions and features while building websites.
MDN DOM
Document Object Model (DOM) contains an introductory guide describing what the DOM is and how it is used. The intro guide describes how the DOM is a programming interface for web documents which represents the page as nodes and objects so that programming languages can interact with the page. The main page on DOM also contains a list of interfaces and outdated interfaces, as well as information about HTML DOM and SVG DOM. This information is very useful for learning JavaScript, as JavaScript works by manipulating elements through the DOM. Each element in an HTML document is represented by as an object in the DOM. I am sure I will reference this guide again while I continue to learn JavaScript.
MDN JavaScript
JavaScript contains an introduction to JavaScript, what programs typically use it, what it is capable of doing, and how the web standards for JavaScript are set. There are links to the JavaScript guide, which gives an overview of the programming language; the JavaScript reference, which contains lists of facts, properties, and concepts related to JavaScript; tutorials for complete beginners up to intermediate and advanced programmers; and references for standard objects, expressions and operators, statements and declarations, functions, and classes. This information can be used to learn the basics of JavaScript and continue learning more advanced functions and techniques. It will be an important resource to keep referencing as I continue to learn the language and how to use it.
Summary
Trusted resources are very important when seeking programming help, as a trusted, reliable resource will provide the most accurate information that is factually correct and up to current web standards. Seeking programming and coding help from individual users can be helpful, but you may also be receiving inaccurate information or improper methods of writing programming functions. A user on a forum is not as reliable as a website composed of knowledge from respected and established developers. It doesn't hurt to get opinions from other developers online, but they should not be relied upon as an ultimate authority when it comes to programming.