My BillboardGui in players head won't work, help?!

I tried to make a billboard show up above players head when they enter the game. But for some reason it says that "Character" is a nil value. Also another problem i thought of is when the player resets the billboard GUI goes away. Please help!

game.Players.PlayerAdded:connect(function(player)
board = Instance.new("BillboardGui",player.Character.Head)
	board.Active = true
	board.AlwaysOnTop = true
	board.Size = UDim2.new(0,10,0,10)
end)

When the player joins, their character hasn't loaded yet. Hence, player.Character is nil (that's where the error you're getting come from).

If you want something to be done each time the player spawns, you could use the CharacterAdded event of the player:

game.Players.PlayerAdded:connect(function(player)
	player.CharacterAdded:connect(function(character)
		board = Instance.new("BillboardGui", character.Head)
		-- You could still use `player.Character.Head`, but just
		-- `character.Head` is nicer
		board.Active = true
		board.AlwaysOnTop = true
		board.Size = UDim2.new(0, 10, 0, 10)
	end)
end)