Something I bumped into today: The first time Internet Explorer loads a URL, it sends an "HTTP_Accept" request header with the list of MIME types it accepts, like so:
HTTP_ACCEPT = application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*
Any subsequent request of the same URL, though, only sends "*/*":
HTTP_ACCEPT = */*
Of course I watched this through an ASP page which wrote out Request.ServerVariables("HTTP_Accept"). I wasn't sure if it was IIS or IE's fault tho, so I checked the raw headers with Fiddler, and it's definitely IE.
What's especially strange is that I can find little or no mention of the problem. Anyone else heard of (or conquered) this?
It rather messes up a page I'm working on...
UPDATE: See here for a bug and workaround demo article I just put together.