The Nielsen Norman Group published an article about the Aesthetic-Usability Effect, which is when users will disregard minor usability issues because the site they are visiting is aesthetically pleasing and visually interesting. The article also touched on how to interpret vague positive comments from research.
Neilsen Norman Group also discusses usability specifically in a separate article. Usability, according to the article, is defined by 5 key characteristics: learnability, efficiency, memorability, errors, and satisfaction. All of these pieces work together cohesively; without one piece, the site doesn’t have ideal usability. Usability also works hand-in-hand with utility, if it provides necessary aspects. If a site has good usability and utility, the site is considered to be useful.
Usability is an important aspect of a website/webpage because if it isn’t easy to use, visitors will not stay long, nor will they want to come back. Marketing and other strategies worked their part in getting visitors there, and usability helps to keep the visitors returning. Usability should be regularly tested, so problems can be fixed quickly and efficiently.