It is worth stressing that design guidelines cannot provide an automatic solution to the design problem. They do not tell designers how to do exactly the right thing or exactly when to do it. Often they are either too specific or too general for a given situation because, to be genuinely useful, they are abstracted from any particular design problem. This reduces their power in any given context, making the guidelines dependent on their user for sensitive and intelligent interpretation. Guidelines are not a stand-alone tool, and they cannot substitute for effective evaluation and iterative refinement within a design. They can, however, provide helpful advice during the design process.
Guidelines emphasize the designer’s need to understand the intended audience and the tasks to be carried out, the need to adopt an iterative design process, the need to gather usability data on user performance, and the need to consider carefully how the guidelines can be applied in specific situations.
Designers cannot use design guidelines alone to achieve an effective design. A guideline cannot recommend one choice over another because each choice depends on many aspects of the situation. Guidelines are often based on informed opinion rather than on established principles. For that reason, guidelines should be viewed as an informal collection of suggestions rather than as an exact science. Designers will have to make many choices on their own and be prepared to test their decisions in the context of their design.
Nevertheless, the benefits gained from following design guidelines should not be underestimated. They provide valuable reference material to help with difficult decisions that crop up during the design process, and they are a springboard for ideas and a checklist for omissions. Used with the proper respect and in context, they are a valuable adjunct to relying on designer intuition alone to solve interface problems.