An error tag is given to an image that includes an artistic error or oversight, usually in the anatomy, but it can be in other elements such as composition or perspective. This can be anything from the obvious: hands with too many fingers (post #1142825) or too many legs (post #71541), to more subtle errors: two left feet (post #1667989), or Tony Taka's disease (post #190107).
Do not confuse error with any of the following, which are for elements that are merely poorly drawn, not outright mistakes:
Don't confuse error with error message.
Generally you should comment on the post describing the error when you find it along with tagging it with error.
The following tags implicate this tag: wrong_feet, wrong_hand, and bad_reflection (learn more).