You should know when the information you are citing was written and/or last updated. It is often difficult to tell for many websites. Look near the location of the title/author (if there is one) or at the bottom of the page for a "last updated" note.
Scholarship in the humanities, social sciences, and "hard" sciences evolves over a considerable period of time not measured in days or months but years. Primary sources in history by their very nature date to the period or event under consideration. All by way of saying that an older source might be appropriate. But in cases where currency is important, such as the need to engage with up-to-date literary criticism or information required to treat patients in clinical settings, think about how the age of the information you have found affects the way you read and accept it. Consider, for example, the difference between an initial review of a novel and a work of scholarly criticism written decades later.