Two months ago Google Adsense launched new ad unit 300X600. About 10 percent of Adsense publishers adopt this ad unit and results a big fail. Sometime 300X600 AD unit do not show full ads and remains emplty. Now Google Launched New Adsense unit 970×90 name as "Super Leaderboard"
Google Adsense New 970X90 Ad Unit Super Leaderboard Launched
IAB Standard "Super Leaderboard" 970×90 ad unit notified by google official blog on 24 April, 2013. Google Adsesne publisher can use this ad unit but only text ads will appear. Personally i am not try this ad unit but many blogger who is my friend try this ad unit and told me the CPC of this ad unit is not so good than 728X90. May be it comes to change in CPC of 970×90 ad unit. I will try soon this ad unit and update this post after. Google Adsense Said in its official blog.
The new super leaderboard ad unit can show up to four text ads organized in a column layout but, as with other ad sizes, the number of text ads per unit may vary per impression. When enabling image and rich media ads for this unit, display ads in the size of a 728×90 unit will be displayed initially. Over time, we expect that the inventory of image and rich media ads for the 970×90 will grow and you’ll see more full-size display ads being served.