[marcinw]

Accept header is all but useless these days. Servers rarely look at the Accept header that is sent with the request, and browsers can rarely know ahead of time what type of content to expect when merely clicking on a URL. Check out this blog post by Eric Law on IE and the Accept Header (http://blogs.msdn.com/b/ieinternals/archive/2009/07/01/ie-an...)

[icebraining]

It depends on whether you're doing a normal website or if it's (also?) a webservice. There are more HTTP clients besides browsers.