Debug message "Resource interpreted as other but transferred with MIME type application/javascript'

OK, I understand what the messages means , but I'm really not sure what's causing it. I'm using Safari and the Web Inspector on Mac OS X, by the way.

Including base64 gzipped stylesheets/images in javascript?

I know you can include css and images, among other file types, which have been stored in base64 form within a javascript file. However, those are decently huge... and gzipped, they shrink down a LOT, even with the ~33% overhead from base64 encoding.