Da' plugin.

Timestamp of when the player voted stored in MySQL table.

Timestamp of last vote is updated via website script.

When a players last vote was more than 24 hours ago, then every time they try to place a block, don't let that block be placed and tell the user they need to vote (a string defined in a configuration file? :>)

If the player is logging in for the first time ever, then they should get 24 hours to play before they have to vote (on first login hook possible? ignore this if it's not really feasible).

Times should be in real-life time, not play-time.

Thanks. <3