Step 1: Use the Best Ad Format

Average CTR by Ad Format
Format CTR
336 x 280 7.46%
300 x 250 5.58%
728 x 90 3.16%
120 x 240 2.99%
160 x 600 2.44%
120 x 600 1.33%
468 x 60 0.53%
The above table makes it very clear which ad format you should be using. The
336 x 280 large rectangle receives the highest click through rate by far. It is followed by
the 300 x 250 small rectangle, and then the CTR really starts to drop off from there.
The reason that these two formats do better than the others depends on which
format you compare them to. The 468 x 60 banner clearly is the worst victim of banner
blindness. Again, “banner blindness” is the fact that most Internet users today are so
used to seeing advertisements that anything appearing in the shape of “tradditional”
web advertising on a page is subconsciously ignored. The 728 x 90 suffers less from
this phenomenon, but it suffers just the same.

The thin and tall formats (120 x 240, 160 x 600 and 120 x 600) get a lower CTR
because they usually don’t fit well anywhere except on the right or left sides of a page.
But the right and left sides of a web page are usually reserved for navigation and
smaller advertisements. The real meat of any web page is in the center of the page.
So while these formats are not bad in themselves, the typical positioning of them gives
them a lower CTR.
Bottom Line: You should be using the 336 x 280 large rectangle format, or if you don’t
have room for that, use the 300 x 250.