when you add the link, do it this way:
CODE
<a href="url here" target="name of iframe">blah</a>
and when you do the iframe, do it like this:
CODE
<iframe name="name of iframe" src="url"></iframe>
and that goes inside your div, like x_angawhomps said.
Hope that helps!!
edit//
if you
do want the entire page to change when you insert a link, use this code:
CODE
<a href="url here" target="_blank">blah</a>
This is useful for having a link
inside your frame that you want to open
out of the frame.