sadly, so far no good:

-in the built-in browser's addons settings it says flashblock "not compatible with microB 3.5"--and it's clearly not working on my n900
-not only that, but after I fully uninstalled it I'm now having some problems: what few other addons I have in the built-in browser now show "error trying to update" when I try to update. . . . so that sucks.

-I thought Noscript was only for firefox--or at least certainly not for the N900 built-in browser (which is why I posted this thread) . . . . but I tried it anyway out of curiosity. And, nope, it does not work.