i don´t know how that question relates to this but ok here are some hints.

1.- why are u using iframe inside a div in the first place?
is it because u are traying to simulate ajax behaviour
is it because u wnat to use the scrool feature of the iframe

either case u should use div only:: Solution is documented in ajax tutorial, and css tutorial elsewhere on the net

2.- Even so here is the solution.
<html......
<div>
<iframe></iframe>
</div>
....

that should handle it, check that u can see the div in the first place, then check if u are actually loading something in the iframe, several techniques can accomplish this, use alert(''), use background-color: ...
borders many stuff possible, if all that fails, try removing ur css definitions cuz u may have a problem with positioning or z-index parameters.

If all that fails rewrite the all thing with order and that should do the job.

3. other cases may be possible but not quite probable.