IAB Interactive Marketing Units (IMU) Guidelines

Latest guidelines from the Interactive Advertising Bureau (IAB) for seven standard ad unit sizes to which publishers are recommended to voluntarily comply.

More information about them, from the website:

The IAB Ad Unit Guidelines are intended for marketers, agencies and media companies for use in the creating, planning, buying and selling of interactive marketing and advertising. The IAB’s Ad Sizes Working Group meets on a bi-annual basis to review proposed new ad units and issue updated voluntary guidelines as appropriate.

Visit IAB - Ad Unit Guidelines and also the handy Display Advertising Creative Format Guidelines: A Quick Reference Guide (also available in excel)