An error page is a webpage that appears when something goes wrong while trying to access a website. It is like a message telling you that there was a mistake or problem, and you cannot see the content you were looking for. Full definition
Double - check that the links you provide on your website actually work — you don't want visitors clicking on links and getting error pages. (webdesignrelief.com)
I apologize if you are one of the ones being sent to error pages when you leave a comment, not sure yet what is wrong! (theinspiredroom.net)