Nice example of the math behind arc HTML canvas arc() from everyone's favorite W3Schools
If you want to paint a triangle and try to fill it some color, remember to draw the three line clockwise or counterclockwise(don't use "contxt.moveTo()" !!!!), or you will fail to fill it.
A good way to learn is by playing around in the W3 examples. Try playing with stroke here.
more about HTML5 video + canvas: Click Here
The Free Software Foundation published an article on Google's shift to webm and stated the following: "Microsoft and Apple support H.264; Mozilla and Opera support WebM and Ogg Theora. For a while, Google has been supporting all of these codecs—but now it's made a bold move to support free standards and drop H.264. That's good news, because if Web video standardizes on H.264, that won't be any better than the situation today. H.264 is a patent-encumbered codec; the MPEG LA organization requires developers who implement it to agree to a patent license. This license is fundamentally incompatible with software freedom. It requires developers to restrict how their software can be used, and to collect royalties in many situations. In order to make sure the Web stays free for everyone, we need a free codec to prevail as the de facto standard with HTML5. WebM can be that codec: Google provides a patent license with the standard that is compatible with free software licenses, and even got the development ball rolling by releasing a free implementation. They're also promoting it aggressively, and their decision to drop H.264 is one more step in that direction." I just thought the article had an interesting perspective, so I wanted to share this excerpt.