Could someone explain the "Flash" situation?

[smhardesty]

OK. I was aware of all the security issues with Flash. I started installing Flash Block in Firefox a long time ago, but just recently stopped. As a matter of fact, I haven't installed it on these laptops with the new Lite install. I was also aware of HTML5 and it's increased use in more and more sites. So there would be my first question. Should I have some sort of HTML5 extension added to Firefox? I know there are 4 or 5 good ones at this point, but I wouldn't know which one I should install, if any. And then my second question would be; Should I still have Adobe Flash Plugin installed in Firefox or should I install a third party alternative? I know there are several players, but I also know a lot of them are no longer being developed, like gnash and lightspark. Or, should I just sit still and wait to see what develops?