The interaction cost is the sum of efforts — mental and physical — that users must deploy in interacting with a site in order to reach their goals.| Nielsen Norman Group
Search engine users click the results listings' top entry much more often than can be explained by relevancy ratings. Once again, people tend to stick to the defaults.| Nielsen Norman Group
When based on user research, personas support user-centered design throughout a project’s lifecycle by making characteristics of key user segments more salient.| Nielsen Norman Group
Responsive design teams create a single site to support many devices, but need to consider content, design and performance across devices to ensure usability.| Nielsen Norman Group
Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.| Nielsen Norman Group