Is establishing an online page with useful books and audio materials considered a waqf (endowment) for me and my parents, and can a supplication be placed on it for visitors to pray for me and my parents for the blessings of this world and the Hereafter?

Creating a website with beneficial books for the dissemination of knowledge is one of the greatest acts of nearness [to Allah]. There is no specific supplication, but one can write: "I ask you to supplicate for me and my parents for the good of this world and the Hereafter," followed by the supplication of the Intimate Friend [Ibrahim]: "{Our Lord, forgive me and my parents and the believers on the Day the account is established}" [Quran 14:41]. If the intention behind "no registration or comments" refers to what is found on websites and forums, there is no harm in it originally, provided it adheres to Sharia guidelines, and it can be done if a legitimate Sharia interest calls for it.