function otevri(url,w,h)
{
	wWidth = window.screen.availWidth;
	wHeight = window.screen.availHeight;
	xpos = ypos = 0;

	if(wWidth > w) {
		xpos = (wWidth - w)/2;
	}
	if(wHeight > h) {
		ypos = (wHeight - h)/2;
	}

	window.open(url, "_blank", "scrollbars=no, toolbar=no, directories=no, top=" + ypos + ", left=" + xpos + ", menubar=no, width=" + w + ",height=" + h + ", resizable=yes");
	return false;
}