Warning

The bottom segment on xkcd.com

The warning on xkcd was originally added to xkcd.com before April 8th, 2006. It used to appear between Randall's list of "Comics I Enjoy" and the footnote, before it was removed on September 12th, 2016. For almost a decade and a half, it served as a humorous advisory message to users about the contents of the comics. It stated:

Warning: this comic occasionally contains strong language (which may be unsuitable for children), unusual humor (which may be unsuitable for adults), and advanced mathematics (which may be unsuitable for liberal-arts majors).

Warning removed

On September 12, 2016, the comic 1732: Earth Temperature Timeline was published and garnered attention from a much wider audience compared to other xkcd comics. Four hours after its release, the warning, along with the previous footnote, were both removed from the site. While a new footnote was added 22 days later, the warning never came back. This new footnote did not include a reinstatement of the original warning message. The removal of the warning and the footnote was likely a result of the comic's sudden surge in popularity, to ensure that new fans were not deterred by the messages.