facebook - Invisible characters - ASCII

Question

Are there any invisible characters? I have checked Google for invisible characters and ended up with many answers but I'm not sure about those. Can someone on Stack Overflow tell me more about this?

Also I have checked a profile on Facebook and found that the user didn't have any name to his profile? How can this be possible? Is it some database issue? Hacking or something?

When I searched over Internet, I found that 200D is an ASCII value with an invisible character. Is it true?

Answer 1

I just went through the character map to get these. They are all in Calibri.

Number????Name???              ? HTML Code ? ?Appearance
------ ???--------------------?  ---------?? ?----------
U+2000 ? ?En Quad ??              ??????" "
U+2001 ? ?Em Quad???              ????? " "
U+2002 ? ?En Space             ?? ???   " "
U+2003?? ?Em Space              ? ????  " "
U+2004?   Three-Per-Em Space      ??   ?" "
U+2005   ?Four-Per-Em Space?      ???? ?" "
U+2006    Six-Per-Em Space      ? ???   " "
U+2007    Figure Space          ? ????? " "
U+2008    Punctuation Space       ??????" "
U+2009    Thin Space            ? ???? ?" "
U+200A    Hair Space            ? ????  " "
U+200B    Zero-Width Space       ​??????"​"
U+200C    Zero Width Non-Joiner  ‌??    "‌"
U+200D    Zero Width Joiner      ‍??????"‍"
U+200E    Left-To-Right Mark     ‎??????"‎"
U+200F    Right-To-Left Mark     ‏??????"‏"
U+202F    Narrow No-Break Space   ??????" "