HTML ads are a type of rich media and are controlled by the same setting as image ads:
"Set your preference for this ad unit: text and image/rich media ads, text only, or image/rich media only."
[
google.com...]
what are HTML ads?
"HTML ads are interactive, customized mini-sites that can appear as Google ads on sites using AdSense for content. HTML ads are a type of rich media ad.
Here are a few important notes about HTML ads:
* Sizes: HTML ads can appear in the same ad sizes that support image ads. For HTML ads to show up in one of your ad units, you'll need to use one of these ad sizes, and also have image/rich media ads enabled for that ad unit.
* Reporting: We'll count a click for each clickthrough a user makes that leads them to the advertiser's site. Depending on the advertiser's implementation, this could be a click on a logo or explicit URL. "
[
google.com...]
Image ad sizes
Leaderboard (728 x 90)
Banner (468 x 60)
Skyscraper (120x600)
Wide Skyscraper (160x600)
Small Square (200 x 200)
Square (250 x 250)
Medium Rectangle (300 x 250)
Large Rectangle (336 x 280)
On my sites HTML ads have a very low CTR but a high EPC so they pay slightly less on a CPM basis compared to text ads. Fortunately they currently account for less than 1% of total impressions.