How to? Bookmarklets that pops out an iframe within any webpage

Can someone teach me or give me links to resources if you know any?

What I want to do is to use a [COLOR=“RoyalBlue”]href=“javascript:…”[/COLOR] link (bookmarklet/favelet) to pop up an iframe over any webpage on any site.

I sort of knows it involves using JS to append some html (JS and iframe) before the </body> element. Set the div to position absolute. Just need a good tutorial or something.