Google Mobile Advertising Guidelines

6:1 Aspect Ratio
• 300 x 50, less than 7.5k file size
• 216 x 36, less than 4.5k file size
• 168 x 28, less than 3k file size
4:1 Aspect Ratio
• 300 x 75, less than 7.5k file size
• 216 x 54, less than 4.5k file size
• 168 x 42, less than 3k file size

File types:
All images must be in a .JPEG, .GIF, or .PNG format.
Animated .GIF images are also acceptable. However, they must follow the same guidelines and specifications as PC-based image ads.
Markup languages:
To ensure that we're able to display your mobile ad and site to users, your destination site must be written in a supported mobile markup language. We currently support the following markup languages:
• wml (WAP 1.x)
• xhtml (WAP 2.0)
• chtml (imode, etc.)
• PDA-compliant html
Flash image ads:
Flash image ads won't be supported at this time.