W3Schools has been teaching web technologies since 1998. It covers HTML, CSS, JavaScript, SQL, Python, PHP, and more with short lessons, interactive examples, and exercises you can run directly in the browser. Each topic includes a reference section with syntax and examples. The "Try it Yourself" editor lets you modify code and see the result immediately.

Professional developers often criticize the depth of the explanations, but for beginners and for quick syntax lookup, it remains one of the most accessible resources on the web. It is not a substitute for MDN's rigor, but it is faster to scan when you just need to remember how a particular tag or method works. Millions of developers started here.