var p=5;  
var q=Math.floor(Math.random()*p+1)  
switch(q) 
{ 

case 1: 
document.writeln("<a href=\"http:\/\/www.puresky.org\/\" target=\"_blank\"><img border=\"0\" src=\"\/images\/js1.gif\" width=\"270\" height=\"270\"><\/a>");
break; 

case 2:
document.writeln("<a href=\"http:\/\/www.puresky.org\/\" target=\"_blank\"><img border=\"0\" src=\"\/images\/js2.gif\" width=\"270\" height=\"270\"><\/a>");
break; 

case 3:
document.writeln("<a href=\"http:\/\/www.puresky.org\/\" target=\"_blank\"><img border=\"0\" src=\"\/images\/js3.gif\" width=\"270\" height=\"270\"><\/a>");
break; 

case 4:
document.writeln("<a href=\"http:\/\/www.puresky.org\/\" target=\"_blank\"><img border=\"0\" src=\"\/images\/js4.gif\" width=\"270\" height=\"270\"><\/a>");
break; 

case 5:
document.writeln("<a href=\"http:\/\/www.puresky.org\/\" target=\"_blank\"><img border=\"0\" src=\"\/images\/js5.gif\" width=\"270\" height=\"270\"><\/a>");
break; 
} 