For those of us that run websites based on Google Sites, the recent boost in search rankings for HTTPS websites, and the subsequent devaluing of unsecured HTTP websites, may have hurt us.
However, there is no way to enable HTTPS for a Google Site with a custom domain, at least not yet. This would require an SSL certificate for the domain name, something Google does not yet provide. However, HTTPS can be enabled through redirects from the custom domain to Google’s URL scheme.
Is there a workaround? There could be, by using a CloudFlare caching solution.
Sources
http://webapps.stackexchange.com/questions/54463/custom-domain-under-ssl-with-google-sites