aspetat ne ho trovato uno forse migliore con il Math.random()

codice:
function banner() {
};

banner = new banner();
number = 0;



banner[number++] = "<a href=\"http://www.link.it\"><img src=\"img\\ciotole_2.gif\" width=600 height=50 border=1 alt=\"Primo banner\"></a>";
banner[number++] = "<a href=\"http://www.link.it\"><img src=\"img\\ciotole_3.gif\" width=600 height=50 border=1 alt=\"Secondo banner\"></a>";
banner[number++] = "<a href=\"http://www.link.it\"><img src=\"img\\ciotole_4.gif\" width=600 height=50 border=1 alt=\"Terzo banner\"></a>";
banner[number++] = "<a href=\"http://www.link.it\"><img src=\"img\\ciotole_5.gif\" width=600 height=50 border=1 alt=\"Quarto banner\"></a>";



increment = Math.floor(Math.random() * number);

document.write(banner[increment]);{