Are you using any blocking programs/add-ons?

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

If images are missing then check that you do not block images from some domains.

• you can tap the Alt key or press the F10 key to show the hidden Menu Bar temporarily

Check the permissions for the domain in the currently selected tab in "Tools -> Page Info -> Permissions".

Check "Tools -> Page Info -> Media" for blocked images

• select the first image and use the cursor Down key to scroll through the list
• if an image in the list is grayed and "Block Images from..." has a checkmark then remove this checkmark to unblock images from this domain

You can check these preferences on the about:config page and make sure they have the default value.

• permissions.default.image (1)
• network.http.sendRefererHeader (2)

There is Tracking Protection that can block (wanted) content, so check the location/address bar for special icons.

• https://support.mozilla.org/en-US/kb/control-center-site-privacy-and-security-firefox

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block (wanted) content (e.g. Adblock Plus, NoScript, Ghostery, uBlock Origin) always make sure such extensions do not block (wanted) content.

• make sure your extensions and filters are updated to the latest version

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Appearance
• do NOT click the "Refresh Firefox" button on the Safe Mode start window
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

See also:

• http://kb.mozillazine.org/Images_or_animations_do_not_load
• http://kb.mozillazine.org/Websites_look_wrong

FredMcD said

Are you using any blocking programs/add-ons? Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Thanks for starting me up. Sorry to take so long; I couldn't figure how to get to this page. Here's the answer to your question: No, in safe mode, the problem is not there. What do I do next?

Go to the top of any support.mozilla.org web page and press your user icon to see your Mozilla profile. Including your questions and answers.

It could be the work of one of your add-ons. Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control> (Mac=<Command>) <Shift> A)

In the Add-ons Manager, on the left, select Extensions. Disable a few add-ons, then Restart Firefox.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All Of them.

If the problem continues, disable some more (restarting FF). Continue until the problem is gone. After, you know what group is causing the issue. Re-enable the last group ONE AT A TIME (restarting FF) until the problem returns.

Once you think you found the problem, disable that and re-enable all the others, then restart again. Let us know who the suspect is, detective.

All plug-ins and extensions were either already disabled or had been automatically blocked by Mozilla with the exception of Norton which I disabled. There was no change. After the list, I have a question. Plugins, all not running:

 Open H264 Video Codec...Cisco Systems...
 Shockwave Flash / 26.0 r0
 Widevine Content Decryption Module Provided by Google Inc

Extensions, all disabled:

 Norton Internet Security (I disabled this one)
 Acrobat DC-Create PDF
 McAfee Site Advisor (disabled by Mozilla)

Question: I was wondering if I could get to normal by deleting Mozilla/Firefox and all its associated files (plists, if any, etc.) and reinstalled a fresh version, or is there something that will still mess it up? Thanks for putting up with me; it's appreciated.

Did you check all suggestions I posted in my above reply?

You can check the Web Console (Tools -> Web Developer) for error messages about blocked and unsafe and mixed content.

• https://developer.mozilla.org/en/Tools/Web_Console

You can check the Network Monitor to see if content is blocked or otherwise fails to load.

• https://developer.mozilla.org/en/Tools/Network_Monitor

Use "Ctrl+F5" or "Ctrl+Shift+R" to reload the page and bypass the cache to generate a fresh log.

For Cor-el, I was flummoxed at first by the developer section (it's way beyond my knowledge base) but there was a statement in one of the pages I was opening that suggested I go to the upper left and check the information for an email I had open that exhibited my problem. When I clicked on that information section, I found the site was not secure and that I needed to disable protection. Doing that solved the problem for that site. For others, I'll have to check each one, I'm assuming. Thanks!

stanbh said

When I clicked on that information section, I found the site was not secure and that I needed to disable protection. Doing that solved the problem for that site. For others, I'll have to check each one, I'm assuming.

This doesn't sound like a good thing to have to do. Do you notice a pattern with these emails? For example, do they have embedded videos? Normally pictures do not trigger a mixed content block.

jscher2000: Thanks for your concern. Almost all of these errant emails are commercial sites, and some are from organizations/associations. For example, a commercial site that I have worked with for well over 10 years: their emails used to display everything but stopped doing so (along with many others) a few months ago. As I said in earlier messages, this problem does not occur on other computers I own, just on this one laptop. The other computers have the very same Firefox version number for Macs. I have also noted that in Norton, which Comcast makes us load, even Apple's Safari is considered a non-secure site SOME of the time, on any of the computers when I open that browser. (But, Safari never has this problem that Firefox has on the one computer.) I should also say that a few other sites of the same type do not have the problem. But, the problem was seemingly increasing which brought me to Mozilla for help.

Is this about Tracking Protection or about mixed content?

Cor-el: if you open the upper left corner where there is a circled i, a shield, a slashed text box (?) and a padlock, you see "Mozilla Foundation," "Tracking Protection," and "Permissions" listed. I don't see anything about mixed content. It is the "Tracking Protection" that I disabled. The graphics involved are always still images, never video. Mastheads in emails usually display just fine, but their additions that specify products, for example, are blank frames. For organizations and associations or foundations, there is usually a new image they are embedding that is blanked with the empty frame and the broken image icon in UL corner. Maybe that's what you mean by mixed content? I'm not a developer nor engineer, so things are sometimes Greek to me.

Mixed content means you're on an HTTPS page and there is some content in the page that was called over HTTP. Thankfully that is not what you're describing.

As cor-el guessed, you are turning off tracking protection for the page. Tracking protection blocks content from certain servers known to be used for tracking your browsing. Or in this case presumably reporting back to the sender that you opened their message. It seems you don't have much choice if you want to appreciate the full message.

HI

For your privacy and security, I have obscured your email address in your question.