1. A method to select images for a markup language document, the method comprising: encoding an instruction in the markup language document, the instruction to be executed by one or more processors to select an image for insertion into the markup language document; selecting a pre-determined number of images from a group of images, the pre-determined number of images being specified in the instruction; and placing the pre-determined number of images in the markup language document at one or more locations defined in the instruction.