If your app absolutely has to have a particular HTML5 feature in oldIE then have look through this list of
HTML5 Polyfills. If your app is more convenient if a browser has a particular feature but can be made to work without then consider your target audience and ask yourself if the effort will be worth the award (remembering that extra processing the browser has to do to implement a polyfill is going to slow it down, and if it's IE8 it's probably already the slowest browser of any your users will be using). HTML5 may be new on the buzzword scene, but it doesn't invalidate the principles of
Progressive Enhancement which were first proposed in 2003.
