while(true){
aleatorio = Math.random();
numero = Math.round(aleatorio * 4);

if (numero == 0){
imagen = "http://img810.imageshack.us/img810/7563/pmabf.png";
break;}

if (numero == 1){
imagen = "http://img440.imageshack.us/img440/9683/pmagh.png";
break;}

if (numero == 2){
imagen = "http://img686.imageshack.us/img686/3493/pmalbp.png";
break;}

if (numero == 3){
imagen = "http://img84.imageshack.us/img84/7151/pmamw2.png";
break;}

if (numero == 4){
imagen = "http://img198.imageshack.us/img198/9606/pmardr.png";
break;}

}
document.write('<a href="https://pmaclan.forumieren.de/" target="_self" ><img src="' + imagen + '" border=0 style="width: 900px; height: 400px"></a>');