No Padlock in Safari
Tony Still I noticed the other day that Safari was not showing a padlock icon in the address bar for secure connections (HTTPS rather than HTTP). Clicking on it let you examine the underlying certificate. I checked Safari's Help and that described how it has always worked.
Today I noticed it again and set out to bug-report it. However, Safari's Help has changed: the padlock has gone, replaced by "Not Secure - " in front of the address for the ever decreasing number of pages that aren't secure*.
If you want to inspect a site's certificate, choose Safari > Connection Security Details... If you want to read the Help page, search for the word Certificate and choose the one called 'Avoid fraud by using encrypted websites in Safari on Mac'.
*In my brief exploration, this mechanism isn't entirely reliable. It sometimes misses flagging the first page you visit, appearing if you move on through the site