(Testing performed with builds as of 2005-04-22.)

Common to all browsers tested:
U+9 - U+d delimits tag names from attributes
U+20 delimits tag names from attributes
U+2f delimits tag names from attributes
U+3e delimits tag names from attributes

Gecko:
U+0 delimits tag names from attributes
U+8 delimits tag names from attributes
U+3c delimits tag names from attributes

IE:
U+0 - U+8 created no element
U+e - U+1f created no element
U+21 - U+2e created no element
U+30 - U+3d created no element
U+3f - U+d7ff created no element
U+e000 - U+ffff created no element

Safari:
U+0 - U+8 delimits tag names from attributes
U+e - U+1f delimits tag names from attributes
U+100 - U+d7ff delimits tag names from attributes
U+e000 - U+ffff delimits tag names from attributes
U+21 - U+2c created no element
U+3b - U+3d created no element
U+3f - U+40 created no element
U+5b - U+5e created no element
U+60 created no element
U+7b - U+ff created no element