IAB announces html5 ad spec recommendations

Even though

it is too early to declare a guideline or specification for HTML5 ads

They are just coming short of doing this.
Display ads should have a border, live in an i-frame, be 75-100k including fonts and libraries, etc.

http://www.iab.net/about_the_iab/recent_press_releases/press_release_archive/press_release/pr-050613