I think
you should use something like this code, it will work fine
<script language="JavaScript">
var UserBoard = new Array(20);
for(var i=0;i<=21;i++)
{
UserBoard[i]=new Array(20);
}
for(var i=0;i<3;i++)
{for(var j=0;j<3;j++)
{UserBoard[i][j]=i+'.'+j;
}
}
alert("test:" + UserBoard[1][1]);
for(var k=0;k<3;k++){for(var l=0;l<3;l++)
{
document.write('(' +UserBoard[k][l] + ') ');
}
document.write('<br>');}
</script>
Please nite that you are having one equlaity instead of assignment in line two.. and store two dimensional arrays like arr[i][j] instead of arr[i,j].