Card sorting is a technique that many information architects use as an input to the structure of a site or product. It’s a user-centered design method for increasing a system’s findability. The process involves sorting a series of cards, each labeled with a piece of content or functionality, into groups that make sense to users or participants.

You should use card sorting because its a quick, inexpensive, and reliable method, which serves as input into your information design process. Card sorting generates an overall structure for your information, as well as suggestions for navigation, menus, and possible taxonomies.

Structure/Navigation Mistakes:

No Structure-when designers treat a site like one big swamp with no organizing principle for individual items.

Missing Category Landing Pages-sites forego the overview page and simply offer links directly to individual pages within a section.

Uncontrollable Navigation Elements-anything that moves and bounces detracts from Web usability; when navigation moves while users are trying to find their way, it’s deadly.

Inconsistent Navigation-Users should be able to understand it immediately, and apply that understanding throughout the site.