var imm = new Array();
imm[0] = "http://www.analisiqualitativa.com/images/advertising/advertising001.gif";
imm[1] = "http://www.analisiqualitativa.com/images/advertising/advertising002.gif";

var lnk = new Array();
lnk[0] = "http://clk.tradedoubler.com/click?p=71740&a=1812120&g=1784944";
lnk[1] = "http://clk.tradedoubler.com/click?p=71740&a=1812120&g=1784944";

var x = 0;

var mostra = document.getElementById("advertising");

function mostra_advertising()
{
    mostra.innerHTML = "<a href='" + lnk[x]  + "'><img src='" + imm[x] + "'></a>";
    window.setTimeout("mostra_advertising()", 13000);
    imm.length - 1 == x ? x = 0 : x++;
}