This error found on some page :

There are php errors or Drupal messages on this page, preventing boost from caching. ERROR:
Array

[type] => 2
[message] => chmod() [function.chmod]: No such file or directory
[file] => /var/www/sites/mysite/mysite.com/subdomains/www/html/sites/all/modules/cacherouter/engines/file.php
[line] => 102