On 2/12/16 Google announced that it would soon stop supporting the Picasa program and the Picasa Web Albums (PWA) website. They planned to move their PWA users to Google Photos. (They previously had tried moving everyone to Google+.) Picasa Web Albums provided more function than Google Photos and would have been my preferred album website if it were not being deleted. Hopefully Google will address this "function gap" problem eventually, but they don't seem to be moving too fast.
Given Google's announcement of PWA's pending demise, I converted all my photo links to now use Google Photos. As of now, August 2016, PWA appears to have finally bit the dust.