this solution will only work:
if you have control over the content of BOTH pages (the "outer" page with the IFRAME tag, and the "inner " page being displayed in the IFRAME)
if the outer and inner pages are being hosted on the same domain (and it's a little less work if they are on the same server)
The solution has two basic steps:
measure the height of the IFrame's content once the content has loaded
set the height of the IFrame to the height of the content
First, let's assume this is your IFrame tag:
<IFRAME
src="
http://myhost.mydomain.com/innerpage.html">