OccupyFlash was the first site and claims that Flash "makes the web less accessible." The site lays out its mission and manifesto of getting people to uninstall Flash from their computers - with instructions on how to do it for Windows, Mac, and Chrome browsers.
The site states: "Flash Player is dead. Its time has passed. It's buggy. It crashes a lot. It requires constant security updates. It doesn't work on most mobile devices. It's a fossil, left over from the era of closed standards and unilateral corporate control of web technology. Websites that rely on Flash present a completely inconsistent (and often unusable) experience for fast-growing percentage of the users who don't use a desktop browser. It introduces some scary security and privacy issues by way of Flash cookies."
To counter the site, OccupyHTML was created - using a similar layout and terms.
This site believes that Flash is still viable despite it not functioning on the Apple mobile platform and counters that "championing simplistic statements regarding web technologies makes the web less educated".
Flash is mature and stable, the site contends, and blames users not keeping installed version updated to avoid crashes. The website admits "it doesn't work well on most mobile devices, and for good reasons. It's a content plugin, developed during the era of closed standards and unilateral corporate control of web technology. Websites that rely on Flash can present a unique (and often unparalleled) experience for the massive percentage of users on a desktop browser. Flash powers some amazing experiences that work consistently across all of the major browsers in a way that cannot be replicated without Flash technology."
The use of the Occupy name for these sites is pure coattailing and could push away the very audience who might have taken sides. Copying the others website design doesn't exactly add credibility to the supporters of Flash.
One amusing note is the domains are owned by people in California - anti-Flash - and New York - anti-HTML5 - so there is even an East Coast-West Coast rivalry going on, though I doubt it will go to the extremes of the rap wars.