Message plus unit
From DigitalJargonBuster
A graphical advertising format for web pages.
Created by the IAB as part of the Universal Advertising Package in 2003, the MPU quickly became a popular format across Europe and North America. Also known as Multiple Purpose Unit. (http://www.iabuk.net/en/1/glossarymtop.html), the MPU now appears to be referred to as an IMU, or Interactive Media Unit (http://www.iab.net/iab_products_and_industry_services/1421/1443/1452)
