TrueView Video Ads are a family of formats that give viewers choice and control over which advertisers' messages they want to see and when. We charge you only when a viewer has chosen to watch your ad, not when an impression is served. Since you pay only when viewers watch your video ad, you can easily increase or decrease your budget depending on objectives.
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.