Access denied on image styles files on Drupal 7.34
It's common to have incorrect permissions on that folder. You'll need to fix the permissions for /site/default/files directory. For a complete answer, see the recommended directory permissions or just run the following from the website root (per @David's comment below).

find sites/default/files -type d -exec chmod 755 {} +
find sites/default/files -type f -exec chmod 644 {} +
chown -R www-data:www-data sites/default/files


For additional issues, check Status Reports on yourWebsiteName.com/admin/reports/status.

Update:

I think I found the issue.

There was a similar question asked on Drupal.

It seems that the issue is that certain hosts, such as BlueHost, HostMonster and Virtualmin forbid +FollowSymLinks. You will need to change +FollowSymLinks into +SymLinksIfOwnerMatch in your .htaccess file. See an entire discussion on Drupal.