Using Firefox 26: Since PBS altered site, receive "An error has occurred ... please check if Private Browsing is OFF" continuously - Private Browsing is OFF.

Question

Have used Firefox many years to view videos at video.pbs.org. Cannot tell which came first: Upgrade to Firefox 26 or PBS making changes to their website but I can no longer view any video at URL: video.pbs.org. As soon as that page comes up, Message dialog window with this text is displayed: "A [sic] error has occurred. For the best experience with this website, please check if Private Browsing is OFF."
If "OK" in dialog is hit, window disappears but reappears in a few seconds. Hitting "OK" on four or five repeats of this message screen results in the message box reappearing but with a checkbox line added with the text, "Prevent this page from creating additional dialogs." Selecting the checkbox makes no difference in the behavior. Dialog box continue to reappear even though a video can be selected and will begin playing until the dialog box pops up. At that time, playback is suspended but resumes after "OK" in hit. Dialog reappears approximately ever 4 seconds.
I have checked the Privacy Options and in about:config that private browsing is not started automatically and is not the default mode or auto started.
I am retired, do not have cable and live in an area where reception of a PBS TV station is problematic so viewing PBS video is my primary TV entertainment option.
Any help would be much appreciated.

Answer 1

When I search in the site's scripts* for this error, it seems to be related to whether the site can use local DOM storage. This is enabled by default in Firefox, but because it is considered cookie-like in nature, blocking cookies on the site will prevent use. So please check the following:
(1) In a new tab, type or paste '''about:config''' in the address bar and press Enter. Click the button promising to be careful.
(2) In the search box above the list, type or paste '''storage''' and pause while the list is filtered
(3) If the '''dom.storage.enabled''' preference is bolded and "user set" to false, double-click it to return its value to true.
Reload the PBS video site and try again. Fixed?
What is your cookie policy? If you have Firefox set to ask you every time whether a site can set cookies or not, I am reminded of an issue that arose in older versions of Firefox (I haven't checked recently).
If you allowed cookies in that dialog, it created exceptions for the full host name (e.g., video.pbs.org) but not the base domain name (e.g., pbs.org). Meanwhile, Firefox was checking whether a site could use DOM storage based on the cookie permissions for the base domain name. So the workaround was to manually create an exception for the base domain name yourself in the Exceptions dialog. You would do that here:
oranage Firefox button (or Tools menu) > Options > Privacy
With "Use custom settings for history" selected, look for the Exceptions button to the right of "Accept cookies from sites"
Not sure whether that is relevant to you. Old threads for reference:
* [https://support.mozilla.org/en-US/questions/934784 Certain websites do not work properly in normal browsing mode but work in private browsing perfectly.]
* [https://support.mozilla.org/en-US/questions/934791 facebook post area when clicked gives https://www.facebook.com/ajax/metacomposer/attachment/status/status.php?targetid=695296250&xhpc=composerTourStart]
''* It is in one of the scripts from the cloudfront''.''net CDN.''