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.
HTML5
HTML 5 is designed so that old browsers can safely ignore new HTML 5 constructs. In contrast to HTML 4.01, the HTML 5 specification gives detailed rules for lexing and parsing, with the intent that compliant browsers will produce the same results when parsing incorrect syntax. Although HTML 5 now defines a consistent behavior for "tag soup" documents, those documents are not regarded as conforming to the HTML 5 standard.