Flash, once the preferred program to run animation and videos (and more) on websites is being seriously challenged by HTML5 with the latter garnering up many of the features and advantages of Flash in a much more fluid and adaptable way. The big killer of course is the smartphone. Most smartphone brands do not support Flash and as more and more users begin accessing the internet through their smartphones, HTML5 gains as a superior option.
More and more websites and web designs are adapting to HTML5, more so when HTML5 itself is in a process of discovering its full potential with more and more features being added. Features that seriously rival benefits of Flash.