If you have a fan page and your visitor who are using secure browsing in facebook get message “This application does not yet support secure browsing (HTTPS)” instead of seeing your fan page tab what that mean?
Secure browsing used to give more security to user from possible threats on internet for their facebook account. As in iframe your fan page tab is not hosted in facebook website that is hosted in your own domain so facebook when give them secure browsing in their server like https://www.facebook then facebook want outside applications also give them secure browsing to make sure they are secure from possible threats.
Solution:
The better solution is call your hosting company and ask them you need secure protocol with shared or private SSL whatever is reasonable for you. If your company do not support https:// hosting you have to move your hosting some other company.
Once you get https:// hosting just copy files from http://www.yourdomain.com/fanpage/ fanpage folder to https://www.yourdomain.com/fanpage/ and paste this URL in your iframe application’s secure browsing url tab that will solve your issue.
If you have any question please post below.