Jfif is the umbrella image format under which Jpg exists, but most applications can't understand or open Jfif files. This issue will be resolved in a couple of weeks when Firefox 3's code is ...

Do not open a jfif in MS Paint or Photoshop and bother resaving it. Just click on the file name, press backspace four times, type jpg (or jpeg), and hit Enter. You now have a perfectly usable image.

Click to see full-sized image. Not sure what purpose it serves, but Firefox 3 on OS X changes the names of jpg files to jfif, which is the umbrella filetype for JPEG encoded files. As a blogger ...