... unchecking Enable JavaScript […] produces some symptoms similar to those you report, but that would've knocked out so much browser functionality that I would expect you to have divined the problem rather quickly.
Indeed, especially since JavaScript is an obvious variable to check, but other than for testing purposes has been enabled all along. And as to Artie’s comment re extensions, they were re-downloaded & reinstalled as part of my efforts to get to the bottom of this, but to no avail.
I’d like to reiterate that the problem is both Safari and user account specific; other browsers I tested in the same user account, like Chrome, Firefox and Opera (all latest versions), do not show it under Yosemite nor do they (in appropriate versions) on the PPC Mac under Leopard. The problem doesn't exist in other user accounts.
