var NewWin;
function createwindow( url, vwidth, vheight )
{
	var width = 300;
	var height = 100;
	var left = parseInt( ( screen.availWidth / 2 ) - ( vwidth / 2 ) );
	var top  = parseInt( ( screen.availHeight / 2 ) - ( vheight / 2 ) );
	var windowfeatures = " width= " + vwidth + ", height= " + vheight +
						 ", left= " + left + ", top= " + top +
						 ", screenX= " + left + ", screenY= " + top +
						 ", scrollbars=no";
	NewWin = window.open( url, "subwindow", windowfeatures );
	NewWin.focus();
}