Is it permissible to advertise a website for publishing and selling books for a fee, given that the website states that it has no intellectual, religious, political, or moral conditions or prohibitions regarding the content of the published books, and that the author is responsible for their book even if it "contains disbelief," and that some book covers include pictures of women?

If the majority of the website's content does not contradict Islam, then guiding people to it for a fee is permissible. The website's reception of any book does not affect this; the transaction between you and it is lawful, and it is up to the visitor to select beneficial books and avoid harmful ones. The owners of the website must prevent the publication of books that advocate vice and disbelief; otherwise, they will be partners in sin.