Mozilla Developer Network (MDN) - это развивающаяся платформа для обучения Веб-технологиям и программному обеспечению, на котором основан Веб. https://developer.mozilla.org/en/
MSDN https://msdn.microsoft.com/library
Safari Developer Library https://developer.apple.com/safari/resources/
Standard ECMA-262 http://www.ecma-international.org/publications/standards/Ecma-262.htm
w3schools.com - THE WORLD'S LARGEST WEB DEVELOPER SITE http://www.w3schools.com/
WebReference.ru - На сайте находятся справочники по различным веб-технологиям, а также руководства по вёрстке веб-страниц и разработке мобильных приложений. https://webref.ru/
learn.javascript.ru - Современный учебник JavaScript https://learn.javascript.ru/
The Web Hypertext Application Technology Working Group (WHATWG) is a growing community of people interested in evolving the Web. It focuses primarily on the development of HTML and APIs needed for Web applications. https://whatwg.org/
WHATWG - HTML: The Living Standard. A technical specification for Web developers. https://developers.whatwg.org/
The World Wide Web Consortium (W3C) is an international community that develops open standards to ensure the long-term growth of the Web. All Standards and Drafts. https://www.w3.org/TR/
The World Wide Web Consortium (W3C) HTML Editor’s Draft http://w3c.github.io/html/
Chrome DevTools Keyboard Shortcuts Reference https://developers.google.com/web/tools/chrome-devtools/shortcuts
Mozilla Hacks - the Web developer blog https://hacks.mozilla.org/
Методология БЭМ https://ru.bem.info/methodology/
High-level advice and guidelines for writing sane, manageable, scalable CSS by Harry Roberts https://cssguidelin.es/
uBlock Origin https://chrome.google.com/webstore/detail/ublock-origin/cjpalhdlnbpafiamejdnhcphjbkeiagm
Session Buddy https://chrome.google.com/webstore/detail/session-buddy/edacconmaakjimmfgnblocblbcdcpbko
PerfectPixel by WellDoneCode https://chrome.google.com/webstore/detail/perfectpixel-by-welldonec/dkaagdgjmgdmbnecmcefdhjekcoceebi
https://www.w3.org/wiki/Graceful_degradation_versus_progressive_enhancement
https://www.youtube.com/playlist?list=PLNYkxOF6rcIBDSojZWBv4QJNoT4GNYzQD