EDIT This is what you get to represent invalid data.

(i.e. Since the Latin1 0xDF (ß) is invalid UTF-8, a correct thing for a display system to do is send the old black diamond [◆] with question mark [?]. )

Cruizing around in Firefox will show you more of these than MSIE, which tries to guess the intended encoding of pages.
 
EDIT Synonyms

Replacement, Replacement Character, Invalid UTF, Invalid UTF Encoding, Ivalid Data Character

 
 
ADD NEWSIMILAR CHARACTERS
 < CHARACTER >  BLOCK PROPERTIES
U+FFFD REPLACEMENT CHARACTER
DEUTSCH : ENGLISH