Google and Microsoft have recently announced that their future browser offerings will rely on HTML5 in favour of Flash.
While it took 17 years for HTML5 to be implemented (since it's predecessor, HTML4), it has become a global staple for developers and brings so much native capability to the browser that was only previously available through components such as Flash or Java.
Flash has been around for a long time and has been heavily used across the internet to provide media rich experiences in the browser. The introduction of HTML5 now means multimedia capabilities are natively available in the browser and Flash is needed less and less.
Furthermore, it is clear that Flash has vulnerabilities which can actually do harm when used in a browser. I know that I have not used Flash in a website in years. Instead, I work with the HTML5 canvas or CSS3 to produce animations and other multimedia effects.
There is also the famous post by Steve Jobs titled "Thoughts On Flash" which helped to usher in the era of HTML5.
I think Microsoft and Chrome's announcement to embrace HTML5 and not support Flash is a great idea. But it does leave a lot of work for developers to do with websites that include Flash.