var banner= new Array()

banner[0]="fondo/a1.jpg"

banner[1]="fondo/a2.jpg"

var random=Math.floor(2*Math.random());

document.write("<style>");

document.write("body {");

document.write(' background: #FFFFFF url("' + banner[random] + '"); background-attachment:fixed;');

document.write(" }");

document.write("</style>");