I developed a web app that responds with data in the format as specified by the client in the HTTP Accept Headers. Everything worked fine while using Firefox, but when I wanted to check my CSS / HTML on Chrome and IE, both of them wanted to download the index page, as if it’s an unknown content type.
After some research I found this article, which states that IE sends out a lot of crud in it’s HTTP Accept headers, amongst others a list of image/* content types right at the start.
This caused my web app to try to send the index page as an image/jpeg.
So how do I know when to ignore and when to use the Accept Headers?
The best thing to do is likely to apply your own server-side weight if there are types with the same weight in the accept header. Thus if you have text/html and image/* both with the same q-value (or none) you could give text/html preference by default.