mik, show us your bangers, luv.
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if you're dead set on using frames/iframes…
iframes are no-go in XHTML 1.0 Strict, so you're looking at an XHTML Frameset (w/ appropriate DTD) housing XHTML 1.0 Transitional pages.
Beyond that, it's pretty much business as usual (given that you're already familiar with building XHTML Transitional pages)