There are some cases where the website can prevent you from accessing certain content when you have the Do not track preference selected. Mozilla has no power over this if this is the case in your specific situation.

If you have third party privacy extensions installed on Firefox (such as an ad blocker), these can also block certain content. If you are using a Private Browsing window or have Firefox set up to always use What happened to Tracking Protection?, then these can also block certain parts of a website.

Hope this helps.

Thank you Wesley for you time and effort. I still need more clarification as I think there is a slightly different nuance here. See below. I do NOT have any 3rd party privacy extensions, am NOT using Private Browsing but do enable Tracking Protection "always". But this "always" Tracking Protection is a feature I've used for years and have not changed this setting to my knowledge. Up until ~ 10 days ago, I did not have content of websites blocked with Tracking Protection "always". Now, as of ~ 10 days ago, most websites content is blocked. If I use the same URL on Mozilla vs. Safari, sometimes I get a completely different looking page between the two browsers with dissimilar content - both requesting "do not track me". I also noticed about 2 months ago that I was getting a bubble message, "Enable Adobe Plug-in" request when I visited websites and I had to click, "allow" when asked. Perhaps I clicked something unintended, like, "never allow"??? Just can't figure out why all of a sudden website content can't be seen by many websites. Was there a global policy change for website tracking or did I click an unintended option for plug-ins? Thank you for your response in advance.

You can check in the Web Console what content is blocked by Tracking Protection.

• "3-bar" menu button or Tools -> Web Developer
• https://developer.mozilla.org/en/Tools/Web_Console

Note that Tracking Protection is a builtin content blocker in Firefox and the do-not-track feature only sends a DNT=1 header to the server and the server decides what to do.

It's normal for Tracking Protection to block the content on certain websites and sometimes even deny you access altogether. This is usually because Tracking Protection has blocked ads from appearing on their website, so they prevent you from seeing certain things on their website until you disable Tracking Protection.

Thank you Wesley and cor-el.

@Wesley I understand advertisements aren't displayed when tracking is on.

I realized that enabling "do not track me" is hindering me more now than in recent times, so I had to allow tracking, which I'm not happy about. I also had troubles with PDF not displaying which is not a tracking problem and I found a solution here: https://support.mozilla.org/en-US/kb/pdf-files-are-blank-or-cause-error-message-mac

Hope this helps others.

Tracking Protection will only block content that comes via a server that is on its block list. This can be advertisements, but also wanted content in case a website uses a server that is on the black list. Always be aware that wanted content can be blocked when you see the shield icon or use other content blocking extensions and in case of issues then disable blocking.