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Well, mangahelpers seems to have purchased two SSL certificates some time ago but the implementation of HTTPS has never been completed.
Right now there are certificates for mangahelpers.com and www.mangahelpers.com but the static(.mangahelpers.com ) subdomain is missing one which makes the usage the other two fairly pointless. You should either provide a fully encrypted channel over HTTPS or let it be.
If you can't purchase another certificate than I suggest to stop using static.mangahelpers.com and any other subdomains without a certificate and transfer all filles to a folder on (www.)mangahelpers.com.
Best would be to implement HSTS as well but the above would already be a good start.
P.S.: You may want to start thinking about implementing IPv6, too.
I will first answer the IPV6 part. We were using ipv6 with vb(3) but I had to disable it because vbulletin(4) has issues with it. I am hoping everything will be fixed soon or is already fixed.
The https was only meant to be used for admin pages. I'll add to rewrite to redirect out of https page.