a = 6;
var slump = Math.random();
var talet = Math.round(slump * (a-1))+1;

function create() {
this.src = '';
this.href = '';
this.border = '';
this.alt = '';
}

b = new Array();
for(var i=1; i<=a; i++){
b[i] = new create();
}

b[1].src = "/img/adv1.jpg";
b[1].href = "";
b[1].border = "0";
b[1].alt = "";

b[2].src = "/img/adv2.jpg";
b[2].href = "";
b[2].border = "0";
b[2].alt = "";

b[3].src = "/img/adv3.jpg";
b[3].href = "";
b[3].border = "0";
b[3].alt = "";

b[4].src = "/img/adv4.jpg";
b[4].href = "";
b[4].border = "0";
b[4].alt = "";

b[5].src = "/img/adv5.jpg";
b[5].href = "";
b[5].border = "0";
b[5].alt = "";

b[6].src = "/img/adv6.jpg";
b[6].href = "";
b[6].border = "0";
b[6].alt = "";

var visa = "";

visa += '<a href=' + b[talet].href + ' target="_blank">' + '<img src=' + b[talet].src + ' border="0"' + ' alt=' + b[talet].alt + '></a>';