For most web technologies, this is a decent source: https://developer.mozilla.org/ https://developer.mozilla.org/ For JavaScript: http://eloquentjavascript.net

For most web technologies, this is a decent source: https://developer.mozilla.org/ https://developer.mozilla.org/ For JavaScript: http://eloquentjavascript.net/ http://eloquentjavascript.net/ For HTML/CSS specifically, use Chrome or Firefox's Inspect Element to take a look at web pages. It's especially instructive to examine things like 1kb grid, where the CSS itself is designed: http://1kbgrid.com/ http://1kbgrid.com/