In my experience we have not had any problems with placing display advertising in IFRAMEs.
- We still have ads that display
expanding content over the rest of
the page. For this to work, it
requires the company delivering the
creative to support "iframe busting"
which does require you to host a
special file on your web server.
Pointroll, Eyewonder and the like
support this. The actual calls to the
ad network (doubleclick in our case)
don't change really. Note that we have a policy of allowing expandable IFRAME content only on user-click; perhaps that is a key factor that enables this technique.
- I'm not sure
what a "combined campaign" but I'm
not sure how it'd be impacted. Our calls to Doubleclick don't change - all the same parameters are supported in terms of identifying the site, zone, location, size, tile etc.
We moved to an IFRAME model from Javascript mostly for the freebie "asynchronous" aspect of IFRAME loading and also because it acts as a sandbox; we found cases where faulty ad creative could overwrite our whole DOM and blow up the page on certain browsers.
There are now techniques that can be used to load content via Javascript and still be asynchronous (XHR injection) but its not for the faint-of-heart and is likely to be incompatible with ad serving anyway due to the need to serve content off the same domain.
Note that moving to IFRAMEs won't reduce page load time as measured by any kind of browser plugin, but it will at least background-load the ads meaning the browser won't halt rendering for the Javascript. We've also experimented with techniques that utilize Javascript to defer the enabling of the IFRAME src parameter until a time that we're ready to let the Ads start downloading (for example, after the above-the-fold parts of the page have rendered). However, its a fine balance between showing the paying Ad content and your page's main content.