var how_many_ads = 4;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads;
ad +=1;
if (ad==1) {
img="images/theme_01_globeman.jpg";
}
if (ad==2) {
img="images/theme_02_suitcase.jpg";
}
if (ad==3) {
img="images/theme_03_pulling.jpg";
}
if (ad==4) {
img="images/theme_04_ladder.jpg";
}

document.write('<img src=\"' + img + '\" width=\"760\" height=\"170\">');