function rotace()
{
var seznam = new Array ("middle13.jpg","middle14.jpg","middle15.jpg","middle16.jpg","middle17.jpg","middle18.jpg","middle13.jpg","middle14.jpg","middle15.jpg","middle16.jpg","middle17.jpg","middle18.jpg");
var pocet;
var vyber;
var cesta;

pocet=seznam.length;
vyber=Math.round(Math.random()*(pocet-1));
cesta="../grafika/"+seznam[vyber];
document.write('<img src="'+cesta+'">');
}