Hi Mathew

For IE8 you can't completely drop Flash, because it has no built-in support for playing back audio or video. But that should be the only time its use is required. You might choose to use it in other instances e.g. for creating animations, simply due to better performance over animating with JavaScript in this browser.

For IE9 there shouldn't be any reason you still need to use Flash. Again, you might choose to include it for specific functionality e.g. for fullscreen video support which isn't available in HTML5 video in IE9.