Untitled

<!DOCTYPE html>
<html>
<head>
	<title>Jogo do galo</title>
</head>
<style type="text/css">

	table{
		margin: auto;
		border: 3px solid black;
		border-collapse: collapse;
	}

	td{
		border: 3px solid black;
		border-collapse: collapse;
		width: 100px;
		height: 100px;

	}

</style>
<body>
	<table>
		<tr>
			<td id="1" onclick="marca()"></td>
			<td id="2" onclick="marca()"></td>
			<td id="3" onclick="marca()"></td>
		</tr>
		<tr>
			<td id="4" onclick="marca()"></td>
			<td id="5" onclick="marca()"></td>
			<td id="6" onclick="marca()"></td>
		</tr>
		<tr>
			<td id="7" onclick="marca()"></td>
			<td id="8" onclick="marca()"></td>
			<td id="9" onclick="marca()"></td>
		</tr>
	</table>
</body>
<script type="text/javascript">

	var v=parseInt("1");

	function marca(x){

		if (v==1) {
			document.getElementById('x').innerHTML = "X";
			v=0;
		}

		else{
			if (v==0) {
				document.getElementById('x').innerHTML = "O";
				v==1;
			}
		}
	}

</script>
</html>