Design Pet Peeve #5: Let’s address the specific design principal of Consistency: The use of elements the same throughout a system no matter where or how they are employed; and how the lack thereof can cause stress, frustration, and sometimes dangerous situations.  Since I spend a great deal of my design time on signs, I will use them as my examples.  Traveling by car to a new destination without the aid of an accurate GPS unit can be highly stressful.  If your destination is a major attraction such as a specific spot within an airport, the signs should lead you right to it, like Hansel and Gretel breadcrumbs strewn on a forest path.  But just as in the fairy tail, sometimes those breadcrumbs mysteriously disappear mid-journey.  And sometimes, the design, color scheme, size, placement, symbology, or text content change from sign to sign or location to location, making the journey all that much more frustrating.