Since usability and user experience have been under scientific examination, guidelines have been established, the so-called usability guidelines, in order to create products that are usable. In the field of web usability the standard ISO 9241 is the most common standard. Also of relevance are Jakob Nielsen’s usability heuristics and guidelines for accessible web content, e.g. the ones of the Web Accessibility Initiative (WAI).
Experts apply these guidelines to improve the user experience, for example, during expert reviews. Since usability guidelines are universal, it is not advisable to simply rely on these rules. After all, they cannot replace usability studies with real users.