The fm:IfUserHasVoted component allows you to check whether or not a user has voted for a particular media item or on the entire vhost.
<fm:IfUserHasVoted mid="123456" >
You have already voted
|The media-id which should be checked for. If 'all' is specified here, we'll check if a user has voted at all on the entire vhost.
|You can optionally specify a date here, if you want to check if a user has voted since a specific time.