var winObj = null

function anzeig(daUrl, wW, wH) { // URL, Fensterbreite, -höhe
        var xPos = Math.floor((screen.availWidth  - wW) / 2)
        var yPos = Math.floor((screen.availHeight - wH) / 2)
        if (winObj != null && !winObj.closed)
                winObj.close()
        winObj = window.open(daUrl, 'daWin', 'width=' + wW + ', height=' + wH
                     + ', location=no, menubar=no, resizeable=no, scrollbars=no,'
                     + 'status=no, toolbar=no, screenX=' + xPos + ', screenY='
                     + yPos + ', left=' + xPos + ', top=' + yPos)
        winObj.focus()
		}