Preserving collections of analogue video art is no easy task. Not only must collection caretakers ensure that their magnetic tapes are appropriately catalogued and stored, they must also properly inspect the content of the analogue videotapes in order to make an informed assessment of their condition. This is the only way to prevent unintended image errors - caused by a damaged videotape or video player, or by simple operator error - from being irreversibly merged with the artist's original image content during the digitisation process and thereby permanently compromising the artwork. This publication aims to provide caretakers of our audiovisual artistic and cultural heritage with a general guide to identifying, viewing, cataloguing and assessing the condition of analogue videotapes. The symptoms and causes of 28 common image errors are described in detail, and further illustrated by video sequences on an accompanying DVD. A technical chapter explains the basic principles of video technology, while an art history chapter discusses the deliberate use of image errors as creative tools in analogue video art.