var newwindow = '';

function displayWindow(url, width, height,parameters,name) {

	var LeftPosition = (screen.width) ? (screen.width-width)/2 : 0;
	var TopPosition = (screen.height) ? (screen.height-height)/2 : 0;

	if(typeof parameters=="undefined" || parameters=="")var parameters="resizable=yes,scrollbars=yes,menubar=no";
	if(typeof name=="undefined")var name="okno";

	if (!newwindow.closed && newwindow.location) {
		newwindow.location.href = url;
	}
	else {
		newwindow=window.open(url,name,' width=' + width + ',height=' + height + ', left='+ LeftPosition +',top='+ TopPosition +', ' + parameters +'   ');
		if (!newwindow.opener) newwindow.opener = self;
	}
	if (window.focus) {newwindow.focus()}

}