HTML5 - Information and samples for HTML5 and related APIs

Test pages

Feature	Web browser support
Canvas	3.0+ 3.0+ 1.0+ 9.5+
Custom data attributes	all all all all all
Custom data attributes - dataset property	none none none none none
File API	3.6+ 4.0+ (partial support) 5.0+
Geolocation	3,5+ (iPhone) 5.0+
localStorage	8.0+ 2.0+ 4.0+ 2.0+ 10.5+
sessionStorage	8.0+ 3.5+ 4.0+ 2.0+ 10.5+
Offline Web Applications	3.5+ 4.0+ 1.0+
Online/Offline events	8.0+ 3.5+ 9.5+
Online polling	8.0+ 3.5+ 4.0+ 5.0+ 10.0+
postMessage	8.0+ 3.0+ 4.0+ 1.0+ 9.5+
Video	3.5+ 4.0+ 1.0+ 10.5+ Notable here is that the main concern is codecs. Firefox and Opera support Ogg Theora, Safari supports H.264 and Google Chrome supports both.
Web Workers	3.5+ 4.0+ 5.0+