Graphics are used on many, if not most, web pages. When used appropriately, graphics can facilitate learning. An important image to show on most pages of a site is the organization’s logo. When used appropriately, images, animation, video, and audio can add tremendous value to a Web site. When animation is used appropriately, it is a good idea to introduce the animation before it begins.
Many images require a large number of bytes that can take a long time to download, especially at slower connection speeds. When images must be used, designers should ensure that the graphics do not substantially slow page download times. Thumbnail versions of larger images allow users to preview images without having to download them.
Sometimes it is necessary to label images to help users understand them. Usability testing should be used to help ensure that Web site images convey the intended message. In many cases, the actual data should be included with charts and graphs to facilitate fast and accurate understanding.
It is usually not a good idea to use images as the entire background of a page. Complex background images tend to slow down page loading, and can interfere with reading the foreground text.
Experienced users tend to ignore graphics that they consider to be advertising. Designers should ensure that they do not create images that look like banner ads. Also, they should be careful about placing images in locations that are generally used for advertisements.
Research-Based Web Design & Usability Guidelines
Use Simple Background Images
Guideline: Use background images sparingly and make sure they are simple, especially if they are used behind text.
Comments: Background images can make it difficult for users to read foreground text. A single, large, complex background image (including a picture) can substantially slow page download rates. If background images must be employed, use small, simple images with ’tiling,’ and/or keep the image resolution as low as possible.
Sources: Boyntoin and Bush, 1956; Cole and Jenkins, 1984; Detweiler and Omanson, 1996; Hackman and Tinker, 1957; Jenkins and Cole, 1982; Levine, 1996; Levy, et al., 1996; Spencer, Reynolds and Coe, 1977a; Spencer, Reynolds and Coe, 1977b; Tinker and Paterson, 1931; Tinker, 1963.
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