People don’t just visit website, they experience it.
Usability is “the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.” (ISO 9241-11)
“In human-computer interaction and computer science, usability usually refers to the elegance and clarity with which the user interface of a computer program or a web site is designed.” (Wikipedia)
“Usability is the measure of the quality of a user’s experience when interacting with a product or system,” whether a Web site, a software application, mobile technology, or any user-operated device.” (Usability.gov)
Website usability is determined by user satisfaction, ease of learning, user ability to remember an organization and its functionalities, user effectiveness, efficiency and likelihood of errors while performing the tasks the site has been designed for. For example, finding the information needed or completing the e-commerce operation.
Usability is very much like quality: you typically notice it only when it is missing.
Sites that are not usable score poorly in:
1. Consistency of presentation and controls across the site
2. Logical and natural organization of information: clear structure, systematic labels, clear and meaningful labels
3. Contextual navigation: how much information is given for providing a context for the user (where is s/he in the site? where can s/he go? how can s/he go back?)
4. Efficient navigation: the amount of time and effort the user needs to exert in order to move around the site
5. Adequacy of feedback: are user interactions clear, are requests answered; do commands elicit the right response?
6. Searchability: how effectively the site content can be sought in search engines.
