var rndnum = Math.round(Math.random() * 10000);
if (rndnum < 5000) {
document.write('<img src="img/landm.jpg" width="347" height="155">');
} else if (rndnum < 7500) {
document.write('<img src="img/landm1.jpg" width="347" height="155">');
} else {
document.write('<img src="img/landm2.jpg" width="347" height="155">');
}