function alternateGridClass (mygrid)
{
	var grid = document.getElementById(mygrid);
	//first row is header, not part of tBodies[] => not changing its CSS class
	for (i = 0 ; i < grid.tBodies[0].rows.length; i++)
	{
		if (i%2 == 0)
			grid.tBodies[0].rows[i].className = 'tdlist';
		else
			grid.tBodies[0].rows[i].className = 'tdnd';
	}
}