:-moz-broken
No estándar: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
Resumen
La pseudo-clase CSS :-moz-broken selecciona elementos con enlaces a imágenes no válidos
Este selector está pensado sobre todo para desarrolladores de temas.