An important clue to whether the information is trustworthy is the publisher, or rather the owner of the website. Details about the owner can usually be found in the section called About us, Background etc., if they are not already shown on the introductory page. If you doubt the quality of the information found, verify from other sources whether the information is correct.
In this example, the website reports on leukaemia and its subpage About WebMD states that the mission of the portal is to inform the public about various issues related to medicine and the healthcare system. Its primary aim is therefore not to provide expert information.
When we compare this website with the preceding example, this one also deals with leukaemia, but the details in the About Us section are more transparent. You can find there information about the financing of the centre, related legislation etc. It follows from both these details and the .gov domain that the National Cancer Institute (NCI) is an institution subject to the US authorities. Therefore, it can be assumed that NCI is subject to various checks regarding whether American legislation is observed and in this respect NCI can be considered to be a trustworthy publisher.
Always ask yourself the following questions: Who is the publisher/owner of the website? What is their aim? If you find that the owner of the website is not a research institution and its target group is the lay public, you cannot reasonably expect to find expert information there. If need be, pay attention to other attributes of the website you found.