var spn = new Array(2);

function inarr(numimg,nomimg){
  spn[numimg] = "immagini/img_st/" + nomimg;
}

function temp_bnr(mx){
var num1 = Math.round(Math.random() * (mx));
var num2 = Math.round(Math.random() * (mx));
if(num1==0){num1=1};
if(num2==0){num2=1};
while(num1==num2 || num1==0 || num2==0){
  var num2 = Math.round(Math.random() * (mx));
}
document.images.bnr1.src = spn[num1];
document.images.bnr2.src = spn[num2];
setTimeout("temp_bnr(" + mx + ")",3000);
return;
}