So, in Internet Explorer 6, go to about:cheese. You'll see that the title bar AND the page now contain the word 'cheese'.
Now type about:<a href="xyz">a</a> in the address bar. Notice that there is now a link in the title bar, and on the main page.
Now try this: about:<iframe src="http://www.google.com"></iframe>. Enjoy browsing google in your title bar.
Note that I was able to use this method to bypass a net kiosk's charging system at a hotel I was recently staying at (create a link to Notepad, use notepad to write an HTML file containing an iframe, then create a link to that file). I ended up setting up all the kiosks to full screen repeat a Rick Roll of the hotel lobby... the PCs had speakers, too... never gonna give you up...