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W3Schools maintains a complete JavaScript reference, including all HTML and browser objects. The reference contains examples for all properties, methods and events, and is continuously updated …

CSS References At W3Schools you will find complete CSS references of all properties and selectors with syntax, examples, browser support, and more.

SQL References At W3Schools you will find a complete reference for keywords and functions:

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PHP References W3Schools' PHP reference contains different categories of all PHP functions, keywords and constants, along with examples.