This can, for instance, be used to draw graphs, make photo composition or simple (and not so simple) animations. The images on the right show examples of implementations <canvas> which they will be in the future in this tutorial. <canvas> was first introduced by Apple for the Mac OS X Dashboard and later implemented in Safari and Google Chrome. Gecko 1.8-based browsers, such as Firefox 1.5, also support this element. The <canvas> element is part of the WhatWG Web applications 1.0 specification also known as HTML5. The HTML5 test - How well does your browser support HTML5? HTML5 Rocks - A resource for open web HTML5 developers.
Even better, each comment can be linked to the related syntax node. This is very helpful since any additional information regarding the program can be provided via the comment serving as a form of annotation.