The performance of HTML5 over Flash on a Mac is much higher and on top of that it uses less battery power in laptops, so it is highly recommended to use it in some of those cases.
The trick is to enable the Development menu in the options to activate the iPad User Agent, something that will make HTML5 our default option on practically all websites that support it.
Anyway, this is not a perfect solution since there are two problems: the first is that if the site is optimized for the iPad we can see it somewhat strange, and the second is that the option only saves it during the current session.
Source | TUAW