When I worked as a copy editor, our goal on the copy desk was always to produce a perfect newspaper. We never succeeded. Most days we were satisfied if no reader complained about an error or made light of one. Yet there were always errors, however minor: misspelled words, misplaced commas, quotes that weren't exactly right, whatever. When you are publishing a newspaper every day, there just isn't enough time to catch every mistake and to double check every fact.
Book editors get more time to read and reread manuscripts and page proofs before publication, yet still errors occur. In Passion for Books, William Keddie tells the story of a Glasgow publisher of fine books in the 19th century that tried hard to produce a perfect book. "Six experienced proof-readers were employed, who devoted hours to the reading of each page; and after it was thought to be perfect, it was posted up in the hall of the university, with a notification that a reward of fifty pounds would be paid to any person who could discover an error," Keddie wrote. "Each page was suffered to remain two weeks in the place where it had been posted, before the work was printed, and the printers thought they had attained the object for which they had been striving."
Yet after publication, several errors were discovered, including one in the first line of the first page.
The Bible is one book publishers try especially hard to make perfect. At one time it could be punishable by death just to publish a new translation of the Bible. Publishing copies that contained significant errors could be more than just embarrassing. Yet in 1611 the so-called He Bible was published, given the name because in one verse Ruth was referred to with the masculine pronoun. Twenty years later a publisher omitted an important not in the Seventh Commandment: "Thou shalt commit adultery." This became known as the Wicked Bible. The Vinegar Bible replaced the word vineyard with vinegar. According to the Unrighteous Bible, the "unrighteous shall inherit the kingdom of God."
Somewhere I have a copy of a now-defunct Christian magazine that, for typographical reasons, would sprinkle large initial letters at the beginning of certain paragraphs. Not until after publication was it noticed that the initial letters across a two-page spread spelled out a common four-letter vulgarism. Yes, it really does happen.
Chance are there is no such thing as a perfect newspaper, a perfect magazine or a perfect book. There are just errors that haven't be discovered yet.