What is the best way to lazy load doubleclick ads

Question

Ads requested via doubleclick often get served from an ad provider network that returns javascript that in turn performs document.write to place ads in the page. The use of document.write requires that the document be open, implying that the page hasn't reached document.complete. This gets in the way of deferring or lazy loading ad content. Putting such code at page bottom is helpful but doesn't do enough to lower all-important "page-loaded" time. Are "friendly iframes" the best we have? Is there any other alternative such as a clever way to override document.write that preserves the proper place in the dom?

Third party ads use document.write to add script and content into the "current" location in a page. The page owner doesn't have control over ad scripts and can't specify a display target div. The ad script expects to write and render at the document position where it is called, so it's not obvious how to position the ad correctly using deferred dynamic script loading. Lazy loading script into context is straightforward, but third-party content rendered in place via document.write is not so easily achieved.

Answer 1

So there seems to be a standard forming around this called friendly iframes (FIF). It feels a bit like a hack but I feel better that the IAB is behind it.

Here's the documentation from the IAB: http://www.iab.net/media/file/rich_media_ajax_best_practices.pdf

It worked for me, and even though you are writing the js dynamically into an iframe, it still allowed the rich media ads to expand outside their space.