Similarly, the ranking of websites by the providers of online search engines, notably of those websites through which undertakings offer goods and services to consumers, has an important impact on consumer choice and the commercial success of corporate website users. Providers of online search engines should therefore provide a description of the main parameters determining the ranking of all indexed websites and the relative importance of those main parameters as opposed to other parameters, including those of corporate website users as well as other websites. In addition to the characteristics of the goods and services and their relevance for consumers, this description should in the case of online search engines also allow corporate website users to obtain an adequate understanding of whether, and if so how and to what extent, certain design characteristics of the website used, such as their optimisation for display on mobile telecommunications devices, is taken into account. It should also include an explanation of any possibility for corporate website users to actively influence ranking against remuneration, as well as an explanation of the relative effects thereof. In the absence of a contractual relationship between providers of online search engines and corporate website users, that description should be available to the public in an obvious and easily accessible location on the relevant online search engine. Areas of websites that require users to log in or register should not be understood as easily and publicly available in this sense.