Can I recommend an article from "A List Apart"?:
http://www.alistapart.com/articles/progressiveenhancementwithjavascript/
When you combine the general approach with that article with useful tools like JQuery (or Prototype, or whatever your JavaScript framework of choice is), it's really trivial to apply the JavaScript behavior after the fact.
There are serveral types of browsers out there that still do not have JavaScript or at least very limited JavaScript support. Not to mention that rule #1 for both WCAG and section 508 compliance (accessibility for non-US folks) is that the sight does not depend on a scripting language to function. If the page reloads every time I make a change, but it still allows me to make changes it is functioning. The AJAX layer on top of the base site makes it possible for me to do the same without the page reloads.
Top reasons I can see for supporting no JavaScript users are:
- Supporting folks with disabilities (screen readers, alternate input devices, etc.)
- Supporting security conscious people: let's face it there's bad people doing heinous things with JavaScript, so the easiest solution is to get rid of JavaScript
- It's the easiest way to disable ads without a plugin
- Mobile and embedded devices
- Command line browsers used to download tools on headless servers
- Search engine spiders only follow real links--JavaScript confuses them
Please, if you are going to require cookies and JavaScript on your site for it to function, then properly do your due diligence to avoid the following problems with the following:
- Cross-site scripting attacks
- 3rd party user tracking
- Hacking/Defacement through DOM manipulation
- Phishing (if a script can access your DOM, it can send any information on the page to the server it was loaded from)
(And that's just the short list)
When the solution isn't that hard, why not do it?
Also, while you're at your JavaScript fiesta, don't forget to support sane keyboard navigation.