var how_many_ads = 7;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads;
ad +=1;
if (ad==1) {
banner="images/header1.jpg";
width="650";
height="200";
}

if (ad==2) {
banner="images/header2.jpg";
width="650";
height="200";
}

if (ad==3) {
banner="images/header3.jpg";
width="650";
height="200";
}


if (ad==4) {
banner="images/header4.jpg";
width="650";
height="200";
}


if (ad==5) {
banner="images/header5.jpg";
width="650";
height="200";
}


if (ad==6) {
banner="images/header6.jpg";
width="650";
height="200";
}


if (ad==7) {
banner="images/header7.jpg";
width="650";
height="200";
}

document.write('<center>');
document.write('<img src=\"' + banner + '\" width=')
document.write(width + ' height=' + height + ' ');
document.write('</center>');