User expectations refers to the consistency that users expect from products. Interaction design is very concerned with this topic. For example, our user expectations for traffic behavior is one of the more consistent ones because it is governed by traffic laws that are enforced. Software, or even worse small consumer electronics, on the other hand, can have widely varying degrees of consistency.
A good rule of thumb or design principle to use in interaction design is to follow the "Principle of least astonishment". In the case of interactive software applications, for example, users form expectations based on their experience with similar kinds of software. Effective software design aims to conform with prevailing norms for aspects of behavior such as the software's user interface and its responsiveness.
A commonly noted sign of poor usability and human factors due to the violation of user expectations is when signs are needed for common things like doors. This was made famous by Donald A. Norman in his seminal book The Psychology of Everyday Things. There is also a website devoted to such Bad Designs [1].