The reply from the host was as follows:
I checked the error logs and didn't see anything stand out, and your permissions all look fine as well.
You can use file manager through cPanel to change the permissions for the directory and files, although they look correct at 755 for directories and 644 for files.
The error log shows these entries:
[Mon Feb 23 07:36:03 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:36:03 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 07:30:54 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:30:54 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/nl/dev_coding_encoding
[Mon Feb 23 07:30:44 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:30:44 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/nl/configuration
[Mon Feb 23 07:30:42 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:30:42 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/nl/cat_cp_page_controls_create
[Mon Feb 23 07:30:40 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:30:40 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/nl/cat_cp_page_controls_categories
[Mon Feb 23 07:29:52 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:29:52 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 07:24:20 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:24:20 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/fr/dev_coding_encoding
[Mon Feb 23 07:24:10 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:24:10 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/fr/configuration
[Mon Feb 23 07:24:08 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:24:08 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/fr/cat_cp_page_controls_create
[Mon Feb 23 07:23:59 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:23:59 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/fr/cat_cp_page_controls_categories
[Mon Feb 23 07:21:43 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:21:43 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 07:18:41 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:18:41 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/es/dev_coding_encoding
[Mon Feb 23 07:18:23 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:18:23 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/es/configuration
[Mon Feb 23 07:18:19 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:18:19 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/es/cat_cp_page_controls_create
[Mon Feb 23 07:18:13 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:18:13 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/gallery/docs/es/cat_cp_page_controls_categories
[Mon Feb 23 07:15:28 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 07:15:28 2015] [error] [client 136.243.5.219] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 06:23:15 2015] [error] [client 157.55.39.247] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 06:23:15 2015] [error] [client 157.55.39.247] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 06:10:57 2015] [error] [client 108.59.8.80] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 06:10:57 2015] [error] [client 108.59.8.80] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 04:57:44 2015] [error] [client 66.249.64.168] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 04:57:44 2015] [error] [client 66.249.64.168] File does not exist: /home/wadiuwan/public_html/robots.txt
[Mon Feb 23 04:18:42 2015] [error] [client 136.243.24.27] File does not exist: /home/wadiuwan/public_html/404.shtml
[Mon Feb 23 04:18:42 2015] [error] [client 136.243.24.27] File does not exist: /home/wadiuwan/public_html/robots.txt