Adobe Flash Player
Steve Jobs also claimed that a large percentage of the video on the Internet is supported on iOS, since many popular video sharing websites such as YouTube have published video content in an HTML5 compatible format, enabling videos to playback in mobile web browsers even without Flash Player.
Video email
Html4 markup language, in use since 2000, doesn't support multimedia elements natively. Html4 email systems typically simulate embedded video in email by having an embedded image (gif) which appears like a frame from a video. Clicking on the image causes a hyperlink to be launched in a browser window to display a video using the browser's video codec or a rich internet application like Adobe Flash. Many codecs and rich internet applications are not natively supported in browsers and require browser extensions to operate which can impede embedded video display.