function set_color(elem)
{
	//alert (document.getElementById(elem.id).style.background)
	if (document.getElementById(elem.id).style.backgroundColor == '#e7e7e7' || document.getElementById(elem.id).style.backgroundColor == 'rgb(231, 231, 231)')
	document.getElementById(elem.id).style.backgroundColor = '#ffffff';
	else
	document.getElementById(elem.id).style.backgroundColor = '#e7e7e7';
}