var m=2;  
var n=Math.floor(Math.random()*m+1) 
switch(n) 
{ 
case 1: 
document.write('<iframe width=760 height=60 src=http://www.14789.net/760.htm frameborder=0 scrolling=no></iframe>'); 
break; 
case 2: 
document.write('<iframe width=760 height=60 src=http://www.14789.net/760.htm frameborder=0 scrolling=no></iframe> '); 
break; 
}