Firebug gives you a way to see deep into the source code. You know when you do view source code you will only see what's directly coded on the page, then when you put a URL through Jutaky's detector it sees what's on the levels 'inside' the source code? Firebug is a kind of mixture of the two, as it's displayed as source code, but you see deeper into the different levels how the detector can, but it's displayed very differently.
It is very hard to learn the firebug and get used to understanding what you see in there. Basically I click the firebug icon then go to the HTML section in there and start opening up those plus marks. If I know there's a 0 iframe in there, I keep opening up those plus marks until I find the 0 iframe code, and then I can even look inside that to see what's in there (like Jutaky's detector will do for you). Another way is if you have a good idea where on the page a problem is, you can right click in that area and choose 'inspect element' from the drop down menu, then firebug will open at that place on the page.
It's very complicated with PTP pages though, and some of the 3rd party codes are very hard to see into and understand - some of them are too complicated for me to understand too.
If you do find a 0 iframe using firebug, what is also important is how you present the information you find, so that others can see exactly where the 0 iframe is, and what it's 'inside'. Because this isn't easy even when you're looking at it, it's even harder when you try to copy and paste, so I'd suggest if you do find anything try to copy as much code as you can surrounding the 0 iframe, so that it might be easier to see what is causing it.
If there's something on a PTP page like this, it is probably from one of the 3rd party ads, it could be something harmless like for tracking, or it could be a bad banner sent out by one of them.
Thanks for being so observant Lynn and your efforts and posting what you find in here and wanting to learn more