Folks on Techmeme are talking about browser-specific sites. The trigger here is a Microsoft showcase page, but it applies just a well to “HTML5 VIDEO” sites which use H.264 codecs, stiffing the most popular “HTML5”-branded browser.
Worse, the increasing complexity and patent costs of the WhatWG’s “HTML5” spec raises a barrier-to-entry for new software… a One-Laptop-Per-Child or $35 Tablet project can no longer afford to create grassroots HTML readers themselves, and will have to go with one of the big, established, and deep-pocketed browser vendors.
Browser-specific features truly Fork the Web.
It’s smarter to add advanced functionality through a common extension to any browser. Even if Adobe cannot quickly create Players for every possible environment, this would still let more people enjoy more functionality more quickly, while still retaining the basic markup which every browser should be able to read.
As a bedrock technology, HTML should be accessible to all. This requires resisting the pressure to make wordly webpages which discriminate against existing and satisfactory browsers.