The internet has become an accepted form of media but until recently, no one has tried to formalize ad sizes. Now, the Interactive Advertising Board has developed voluntary guidelines for online ad formats. The IAB is dedicated to helping online, Interactive broadcasting, email, wireless and Interactive television media companies increase their revenues.

There will always be exceptions to the standards and people are likely to invent new ways to advertise online but having a set of standard shapes and sizes for online ads simplifies both sides of the advertising process. As a website owner, you don’t want to negotiate the banner size every time someone advertises on your site. Advertisers could get much more use from a single banner design if the more frequently they can reuse it.

The IABs guidelines provide a sensible starting point for website advertising specs. The internet is loved for it’s quick innovation so don’t feel hampered. Just make sure you have a good reason to deviate.

IAB standards are as follows:

Rectangles and Pop-Ups

300 x 250 IMU - (Medium Rectangle)
250 x 250 IMU - (Square Pop-Up)
240 x 400 IMU - (Vertical Rectangle)
336 x 280 IMU - (Large Rectangle)
180 x 150 IMU - (Rectangle)

Banners and Buttons

468 x 60 IMU - (Full Banner)
234 x 60 IMU - (Half Banner)
88 x 31 IMU - (Micro Bar)
120 x 90 IMU - (Button 1)
120 x 60 IMU - (Button 2)
120 x 240 IMU - (Vertical Banner)
125 x 125 IMU - (Square Button)
728 x 90 IMU - (Leaderboard)

Skyscrapers

160 x 600 IMU - (Wide Skyscraper)
120 x 600 IMU - (Skyscraper)
300 x 600 IMU - (Half Page Ad)

Yahoo is launching a new ad system, Project Panama, today and I’m hopping it’s a success. Don’t get me wrong. I like Google and think their product is great. I’m not picking sides in the search engine battle. I’m just hoping Yahoo can equal the playing field and give advertisers better results for their dollars.

The much-delayed ad system, known as Project Panama, is Yahoo’s effort to close the wide gap with Google in the race for search advertising dollars, a fast-growing and incredibly lucrative business that Google dominates. As such, Panama is the most important new product for Yahoo in years.

A Long-Delayed Ad System Has Yahoo Crossing Its Fingers - New York Times