var window_width = '0';

function modal_show(id)
{
	document.getElementById("modal_back").style.display = 'inline';
	document.getElementById(id).style.display = 'inline';
}

function modal_hide(id)
{
	document.getElementById("modal_back").style.display = 'none';
	document.getElementById(id).style.display = 'none';
}

function modal_center(id, width)
{
	document.getElementById(id).style.left = (window_width / 2) - (width / 2);
}

function read_width() {
	if( typeof( window.innerWidth ) == 'number' ) {
	//Non-IE
	window_width = window.innerWidth;
	} else if( document.documentElement && ( document.documentElement.clientWidth) ) {
	//IE 6+ in 'standards compliant mode'
	window_width = document.documentElement.clientWidth;
	} else if( document.body && ( document.body.clientWidth) ) {
	//IE 4 compatible
	window_width = document.body.clientWidth;
	}
}