there are really four areas to watch

1) ajax via xmlhttprequest. some frameworks will fallback to iframes but
the microsoft kit no longer does this. this requires your site work
without ajax if security disables active/x or xmlhttprequest is disabled.

2) active/x, java applets or .net components. security may disable these

3) binary behaviors. these are most commonly used in IE for opacity. if
behaviors are disabled, instead of opaque, you get solid black.

4) javascript disabled. you site falls into dumb mode. only asp:buttons
will postback. most of the asp.net server controls require javascript
and have no fallback.

-- bruce (sqlwork.com)