404 - have no clue. Literally: error message 404, address not found.
^5 - (abbreviation) high five; that hand slapping in the air thing American basket-ballers do whenever they score. Just turn on the telly some Saturday afternoon.
** - denotes that the words or (abbreviation) between the asterisks represent physical expression. Usage example: "*sigh*", "*S*", "‘*weg*".
(((((((monkey))))))) - the brackets indicate that a chatter is being hugged, usually in greeting or at parting.