I came from this topic: Iframes and SEO

In response to the "stone age" poster I would say that the iframe has been reinvigorated by the latest craze Web 2.0

iframes are useful when you're creating Ajax web sites when you want the back button to work. Example: GMail

If you don't want the back button to work, you use xmlhttprequest when requesting new data.

And yes, <noframes> is the SEO solution for frames, without that tag, frames would ruin your SEO (see above link)