<table><tr><td></td></tr>
will work on IE, but not on NS (no </table> tag!). The point is: it's safer to use standards, you never know who/what might insist on it.
I'm not sure, but I think that data would get scrambled if you use "text/something" or leave the default ("text/html").
Btw, did you try it on NS?
Btw, jpj is also gif?! What is jpj? (if it's jpg, then it's mime is "application/jpeg")