Half Page Ad Format (300 x 600) is less known Ad format and Google AdSense serves this format only to limited partners. Half Page is a Standard IAB format.
You will see this Half Page Ad only to limited websites and blogs with very high specific audience.
Half Page Ad Format is now an IAB standard Format
Despite the fact that Half Page Ad Format (300 x 600) has become an standard IAB format and those ‘popular formats’ like 336 x 280 has been delisted, Half Page Ad Format is still not for ‘general websites’.
What are the benefits of using from Half Page Ad Format Advertisers’ and Publishers’ side
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Larger the Adverts total area, people will click more, thereby higher CTR. This explains why you get more CTR with 336 x 280 unit than the standard IAB format 300 x 250 unit. You can read our article on Ad Unit size and revenue as well.
Probable problems with Half Page Ad (300 x 600) Unit
As the Half Page Ad unit is attractive itself, there is more change of ‘trial clicks’ by the visitors. So, this unit specifically needs a bit adjustment for its CTR and CPC.
Here is a sample of optimized Half Page Ad (300 x 600) Unit :
The format is jpg, size is 32.5 kb (which maintains the IAB guideline).
Are you an Advertiser or Publisher and interested about Half Page Ad Format?
We are running a pole for this Half Page Ad Format. Options are quite clear and self explanatory.
Your vote is important for this pole. Participate and cast your vote against or for Half Page Ad Format. We will publish the result on this page after a good sample size is attained. Apart from sharing this webpage’s url; you can directly cast your vote via this link.
We will explain the poll result of Half Page Ad Format in another post.
Update : Thanks for participating in the poll. Google AdSense now offers 300×600 unit to any normal AdSense account. This poll had might had something to do to convey the wish.

I guess I will not be able to display Half Page Ad (300 x 600) Unit on my blog any time soon. It’s a shame Google sometimes ignores small business, but anyways it is still the best web advertising program.
You can use Half Page Ad using Double Click for Publishers (DFP). Unfortunately, there are very few Advertisers who have the unit in stock and if they do not have Half Page Ad (300 x 600) in “stock” to show, it shamefully shows 160 x 600 Ads.
After numerous experiments I reached the conclusion the 336 x 280 unit still does the best job for both text and media ads, though it would be nice if new designs are available in the near future.
The new size looks really good.