I spotted some unit that I didn’t see earlier. Here ( http://blog.milandinic.com/2009/02/15/new-adsense-unit/ ) is video with unit in action on link. Is this really new unit or it is new only for me? I searched on web and didn’t find anything about it.
You can't choose would you like to use it or not, it seems it is some Google's testing which places this units randomly.
you must know that there is a maximum limit for ads so you may exceeded that limit, thats why its not viewed.
its related to it. you must know that you can't place more than a limited maximum number of ads in every page.
i just now logged in to my adsense account and checked if they have introduced any new ad format... but no,......its really strange....
It is not new ad format, it is normal 250×250 unit, probably image type (there is that google_ad_slot not google_ad_type so I'm not sure, but after refreshing images are always showed). And it is not flash but normal JavaScript (see that I'm marking text)