Html vs. flash

Hi all forum wanderers

I have tried to find an answer to this question but don’t really know how to search.

I see a lot of comments bagging on websites that are created entirely in flash. I was wondering about the reasoning behind that. I mean, I know nothing about html, and I am learning flash (slowly, but surely). Why shouldn’t I build a site entirely in flash? What is the problem with that? Why is it bad? Or maybe not “bad” but . . . not pc? Is it a space/size/loading issue? Is it the fact that one needs to download the flash player to view the site?

I’d appreciate hearing what others have to say about it!

:?)