Internet Explorer 9 will support the CANVAS tag, making support for the tag ubiquitous across major browsers.
The <video tag>, as defined by the HTML5 spec, is an element "used for playing videos or movies". Which codec those videos or movies are in is currently undefined, with the two contenders being the free open source Ogg Theora and the proprietary H.264. With the unveiling of Internet Explorer 9 both Microsoft and Apple are supporting H.264 in their browsers, and comparisons of the standards seem to bear out H.264 as the better of the two. However Mozilla have taken a stance against incorporating H264 into Firefox on the grounds that it is patented and has to be licensed. Arguments are now being made for and against Mozilla sticking to its ideals. John Gruber of Daring Fireball points out that Firefox already supports proprietary formats such as GIF. Um, perhaps not the best example.