If a Google sites page is opened using the default web address (example:sites.google.com/site/yourname), it automatically uses https:// protocol. Even if you type http:// it changes to https://. This prevents the functionality of certain gadgets inserted into the pages.
The gadgets that use scripts are blocked and not visible, for example the widely used 'include gadget'. The affected pages in this site are Blog, Tamil, Citation and Keyword. Also the Facebook like buttons got disabled.
(However if the site is mapped with own web address (example: www.yourname.com), the http:// protocol can still be used and no problems.)
In order to enable the functionality of such gadgets with https://, the following changes are required in the browsers:
1) Chrome browser: Click the security warning button at the top right corner of your browser and click 'Load unsafe scripts'.
2) Firefox browser: Click the security warning button at the top left corner of your browser and click 'Keep Blocking'>'Disable Protection on This Page'.