Some UX designers (and many clients) aim to "jazz up" the design to supposedly engage users. This usually backfires because extraneous design elements get in the way of users' tasks.
Qualitative usability testing aims to identify issues in an interface, while quantitative usability testing is meant to provide metrics that capture the behavior of your whole user population.
Refrain from opening new browser windows. [...] Carefully examine the user’s context, task at hand, and next steps when deciding whether to open links to documents and external sites in the same or a new browser tab."