A file that's both an acceptable HTML page and a JPEG (view source on it)
trick summary:enter in you jpeg comment field: "...your page...then the "image" will look like:   @^PJFIF^@^A^A^A^A,^A,^@^@000^Cr...your page...<!-- rest of garbage

to the browser this is just the same as:   \n
   \n
   \n
   ...your page...