Summary: banners is the top left corner. If your web page is aligned at the left, the best place is the top right corner. The below image shows the best arrangement for the Adsense ads on a web page: Another important thing is the color of the ad units. Always choose the Default Google Palette if your web page background color is white. Users are used to the blue hyperlinks. Hyperlinks
Image Dimensions: 401 x 429
Image originally found here.