So lets say you have the following HTML snippet:
<html> <frameset rows="20,*" border="0" frameborder="no"> <frame name="menu" src="menu_frame.html" scrolling="no" noresize="1"> <frame name="work_frame" src=""> </frameset> </html>
First of all you would say: but frames are so 1998! And you would be right. Frames are outmoded, deprecated and a usability nightmare (because you can't bookmark the exact state of the frameset), you have to use them in certain situations. Like, for example when providing a "unified menu" in an intranet where you can't (or don't want to) touch all the sub-sites referenced. "The right tool for the right job".
Back to our problem: the page from the upper frame contained a bunch of links targeted at the lower frame in the form of:
<a href="http://www.example.com" target="work_frame">Example</a>
The problem was that while on all "sane" browsers the link opened in the lower frame, Internet Explorer (both version 6 and 7) insisted on opening a new window for the link. Finally I got the idea to create a blank page and set the lower pane to it:
<html> <frameset rows="20,*" border="0" frameborder="no"> <frame name="menu" src="menu_frame.html" scrolling="no" noresize="1"> <frame name="work_frame" src="blank.html"> </frameset> </html>
Magically everything worked. So there you go: IE + Frames = Headache (from banging your head against the desk), or at least Magic.
PS. I never tried using "about:blank" instead of an explicit blank page, which seems to be standard (I don't know if official or unofficial) between the major browsers. Possibly it would also work (and has the advantage that you don't have to explicitly code an "empty" html file).