One of the most com­mon adver­tiser ques­tions in dis­play relates to ad sizes. While there are many sub fac­tors relat­ing to ad sizes such as fre­quency cap­ping, above/below the fold, ad for­mat, rich media, etc., at its core, the ad size itself cer­tainly is an impor­tant fac­tor in any suc­cess­ful dis­play cam­paign optimization.

The five most com­mon Dis­play cre­ative sizes are:

-          120 x 600 (nar­row ver­ti­cal tower)

-          160 x 600 (wider ver­ti­cal tower)

-          300 x 250 (box)

-          468 x 60 (small hor­i­zon­tal banner)

-          728 x 90 (large hor­i­zon­tal banner)

There are many other ad sizes as well, both smaller and larger but we will focus on the inher­ent per­for­mance and deliv­ery dif­fer­ences of the main 5 ad formats.

Fig­ure 1: EF US Client Ad Size Per­for­mance 2010

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His­tor­i­cally, there has been more dis­play inven­tory on pub­lish­ers’ sites in the 300×250 and 728×90 ad sizes due to that for­mat work­ing best with the gen­eral lay­out of pub­lisher web pages. The EF data in 2010 would also sup­port that notion, with 63% of all inven­tory com­ing from those 2 ad sizes.

These sizes also rep­re­sent the ads that have the high­est like­li­hood of being clicked by a browser as well which cer­tainly speaks strongly as a major com­po­nent of how an adver­tiser should opti­mally bid a given ad cre­ative. The 300×250 and 728×90, along with the 120×600 nar­row tower, also have the high­est CTRs.

Now, this does not account for ROI for a given adver­tiser to their suc­cess met­ric or the “qual­ity” or ver­ti­cal of the pub­lisher. The impact of view-throughs (where a con­sumer com­pletes the advertiser’s con­ver­sion goal such as a lead or sale sub­se­quent to being served and view­ing a dis­play ad but not actu­ally click­ing it) is also not encap­su­lated in this data.

The fact that 428×60 ads have the low­est amount of inven­tory and the low­est CTR should be bal­anced against the fact it is also the cheap­est inven­tory to buy judg­ing by EF’s 2010 data. At $0.39 CPM, it is just a bit over one-fifth of the price of the next cheap­est inven­tory size in 2010 being the 728×90 ads.

For any adver­tiser want­ing to opti­mize a dis­play cam­paign suc­cess­fully, they should not neglect any of the major ad sizes as hav­ing more options to dis­play your cre­ative will allow for greater effi­cien­cies. It is impor­tant to note that if you have 5 dif­fer­ent ad sizes, for each dif­fer­ent message/product/special offer/display exchange, etc. that you are pro­mot­ing, the num­ber of bid/ROI per­mu­ta­tions mul­ti­ples very quickly.

Given this, for best results, as well as the abil­ity to test dif­fer­ent mes­sages, a sophis­ti­cated algo­rith­mic and cross chan­nel  plat­form should be uti­lized so you are bid­ding opti­mally each day (and in the case of Real Time Bid­ding, each sec­ond).  Adver­tis­ers need to look at results across all your dig­i­tal chan­nels together, be it SEM, Face­book, etc. as most users are brows­ing across the Inter­net and mar­ket­ing media spend should not be looked at in silos.

Chris Jacob