berto - 9:00 pm on Dec 13, 2007 (gmt 0)

but i think revenue will decrease as it will show more ads in 1 banner

More low-bid advertisers might show (in the scroll-down or scroll-to-the-side displays), but CTR might go up, as the site visitor has more choices. So, it all depends on whether higher CTR offsets lower EPC (earnings per click).

If you didn't think this, if you think that more ad displays by necessity lead to lower overall revenue, then by all means, implement single-ad half banners and buttons on your pages to minimize display of the low bidders.

I don't know about you, though (and I don't recall their EPC, whether high or low), but I do know that half banners and buttons had atrociously bad CTR on my sites, and despite the supposition that only highest bid advertisers occupied those spaces, by posting those ad types I lost revenue.

I also know that link units (not disguised as navigation links, not unduly blended in so as to confuse the visitor) do fairly well on my sites, on a par with ad units. Yet link units potentially display 40-50 ads (depending on whether you show the 4 or 5 links variety, with each follow-on page showing 10 ads per page). Surely there must be many low bid advertisers among those 40-50. But there must be enough high bidders, too, because from link units, I make relatively good money.

Look at it this way: Google is testing scrollable ads to see if, not only will advertisers benefit, but also will Google, and by implication publishers, too. There is a rough correlation between Google's take and ours. If, as a whole, Google's algorithms determine an ad mix/format/presentation that yields the highest average CTR x average EPC, they benefit, and publishers do too. (Another rhetorical question: Does anybody think that Google got rich by purposely maximizing the impression counts of pennies-per-click, lowest-bid advertisers?)

As in all things, you have to find the "sweet spot," in the case of Adsense between too many ads and too few, just the right mix that maximizes ad revenues in your particular situation. Scrollable ads are potentially another tool for achieving that sweet spot.