When would you get a 404 when a page actually exists?

Question

I've got an aspx page with a simple databound datagrid on it; some users get the page just fine. Others get 404s. If there was something wrong with the page, wouldn't I get an asp.net error, instead of a 404?

Answer 1

What kind of 404 is it? (Is it from IIS or from ASP .Net?)

If it's an ASP .Net 404, it's possible (but unlikely) that your code is throwing a fake 404 (search for throw new HttpException)

Do you have a server cluster? If so, one server might have an out-of-date copy.

Answer 2

Do you have any global error handler performing a redirect?

Something in the Global.asax or web.config?

Answer 3

For security reasons IIS6 can send 404 when in fact the result should be permission denied or forbidden. Someone trying to gain malicious access will not be alerted to the existance of a page that they may then concentrate efforts on.

I can't remember if this is default config or needs to be switched on.