html5 built in ipad2?

html5 is the language that is used to code/writ e the video file. It is not "built into" the iPad. It is used in the building of the website. And yes html5 should work on the iPad.

What site could you not access or watch?

If the message that you received is something like, "This player is not enabled for HTML5 delivery", then this actually means that the player on the website does not support HTML5. It does not mean that your iPad does not support HTML5.

The message comes from the web site and is confusing. It is complaining that you don't have Flash. You need to find a "mobile" version of that site that doesn't use Flash.

HTML5 refers to the Hyper Text Mark-up Language version 5 (Draft). The Safari browser on iOS is an HTML5-based browser and scores a 305/475 on html5test.com's HTML5 compatibility test suite -- only Chrome on OS X and Firefox on OS X score higher (340 and 313, respectively). There is nothing for you to install, HTML5 is a built-in part of the iOS operating system.

That said, you are referring to a video webcast. As you are aware, though the HTML5 specification defines a video element for inserting video into HTML5 pages, the specification does not yet specify what video formats should be supported, and most mobile devices (iOS, Android, etc.) have certain limits not only on the format but encoding paramters (resolution, bitrate, frame rate, etc). HTML5 video does permit you to indicate mutliple formats in a single video tag to assure playability of the content, but it's quite possible that the person the created the page did not include a video format compatible with your device (or, perhaps, any mobile device). iOS supports MPEG-4, h.264, and motion-JPEG. Most Android devices will accept a slightly more restricted set of h.264 encodings and WebM (it does vary depending on the model of Android device and the vendor). Generally, most mobile devices support only formats for which there exists a dedicated hardware decoder for the video stream (otherwise performance would be poor and the batteries would wear down very quickly).

Anyway, the most likely explanation is that the page contained valid HTML5 with a valid video tag, but did not reference a video stream formatted properly for playback on your device.

Neither iOS nor Android support adding audio/video codecs to the platform, but both platforms do have third-party applications that can playback a broader range of video formats. Check their respective App stores.

I suspect that the individual/organization that made the HTML5 page available presumed that viewer would be using a desktop system that supports a broader range of audio-video encodings than what is found on contemporary mobile hardware.

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