WebGL, like WebRTC, is one of the new and exciting features to start seeing high quality support on many modern web browsers on desktop and on mobile. Taking advantage of hardware-accelerated graphics on a client's computer or device can enable you to bring many of the fully-featured 2D and 3D animations and interactions you may have used while developing Flash projects in the past. When attempting to verify if the browser you are using supports WebGL, the easiest tool for verification can be found at http://get.webgl.org.
If your browser passed the WebGL verification tests, the site will be displayed as shown in the previous screenshot, rendering a 3D wireframe rotating cube, and the text alerting you of the results. You can of course utilize http://caniuse.com to check what browsers currently support WebGL as well as dig into the official WebGL public wiki found at http://www.khronos.org/webgl/wiki/Main_Page.