Ok, I apologise firstly to the guy who first asked this question 2 months ago. I have been doing quite a lot of research into this question and even managed to contact the web design company whom made the website in question. So the question:
I have found a website which uses IFrames to call in conent, there are multiple fronts to the site for various "shop fronts"... yet it does very well within Google... how is this so? - question has been changed to generalise
The answer isn't so simple, not least because much of the code is hidden away... having delved deeper into this I do have something of an interesting answer though. In essence the developers wanted to include various content on multiple pages and of course didn't want to repeat the content and waste server space and precious loading time. This is a puzzle quite a lot of us have faced ... now with this in mind most (i should add "Silly" here) people will simply use an IFrame to call in the script, but there are multiple issues with this including that the "nofollow" of an iframe is no longer recognised by google, and more importantly that search engines will see the two (or more) pages in question as seperate pages... and if one page is IFramed into another multiple times the external pages is likely to rank higher on Google and therefore appear before other pages.
PHP includes are by far the simplest and best option (and of course there are evil microsoft equivs). Ajax used in conjunction with PHP is by far the best option and makes things look a hell of a lot better, a great example of this can be found over at Headscape. Ajax libaries are amazing tools which make life alot easier, the two I would suggest looking at are JQuery and MooTools ... I also advise you load the libary externally to release load from your server... an example is JQuery from Google Code. Want to see some more simple non js-libary bedded scripts? Head over to Dynamic Drive.