It might just be me, but it sounds like you're asking "how much should I sell my car for" without telling us what kind of car you're selling. Ok, ok, maybe that

It might just be me, but it sounds like you're asking "how much should I sell my car for" without telling us what kind of car you're selling. Ok, ok, maybe that's a bad analogy. Honestly, at this point in my development career when I'm designing a first iteration of a web app, I don't even worry about people with 800x600 rez, or no cookies, or no Javascript. Again, it might just be me, but that's like worrying about scaling to 1 million concurrent users when you're first building your app - not worth the time. Sure, it would be nice, and sure, some gov't agencies (I've worked for one, the Florida Division of Emergency Management) require adhering to some handicapped guidelines. However, you time is valuable. Keep that in mind. You're trying to maximize the total utility to your users, and making 2 complete apps for JS/No JS (a la GMail) isn't maximizing your time. Later, when you have xx,xxx,xxx users - yeah, go for it; you could be turning away thousands of non-JS users. But, let me ask you, do you have 1E8 users? Don't initially spend 20% of your time on 2% of your audience...