you can just use this php code as your index
Code:
<?php $amount = "2"; $url[1] = "http://www.yoursite.com/index1.html";$url[2] = "http://www.yoursite.com/index2.html";srand((double)microtime()*1000000); $random = rand(1,count($url));header("Location: $url[$random]");?>