Interface design revolves around three basic issues: 1) NPS Visual Identity, 2) Accessibility, and 3) Usability.

Visual Identity encompasses two basic graphic concepts: 1)The Messaging project is housed and described at http://www.graphics.nps.gov/ and 2) the NPS ParkProfiles system.

There are several sources for Accessibility issues. For the NPS a first stop is http://www.nps.gov/access/. Another good location is W3C Web Accessibility Initiative (WAI).

Usability is a little broader concept than branding with a corporate logo or accessibility by a visually hearing impaired person (as examples). Usability is the study of how people tend to analyze and interact with objects. A very good site the usable technology site useit.com.