You might be blocking content somewhere.

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?

Yes, I still have the same problems in safe mode. How can I find out what is blocked?

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Go to that message, and use the Undo link to its right.

Please provide public (no password) link(s) that we can check out. No Personal Information Please !

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

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

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, Flash Block, Ghostery) then always make sure such extensions do not block (wanted) content.

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

There is security software that can interfere with loading content, so check that as well.

See also:

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems
• http://kb.mozillazine.org/Images_or_animations_do_not_load
• http://kb.mozillazine.org/Websites_look_wrong

I did most of the above, but I still have the problem. Also, I could not find "about:config" on any menu. If you are referring to Help/About, there is no config on that menu.

You can type or paste about:config in the location/address bar and press Enter to open this page in a tab.

You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

• "about:" is a protocol to access special pages

For the New Tab Page tiles:

Do you notice any pattern to their disappearance? For example, if you use one of the tiles to navigate to a site, then open a new tab, has Firefox successfully captured the thumbnail for that tile? If so, how long does it stick around?

For photos on websites:

I think all of the earlier suggestions cover the usual reasons for the problem. However, if you have had any issues with secure connection errors, or if you get a mixed content notification below the lock icon on site with this problem, we should address those potential issues.

I get the same result whenever clicking on a tile. It does not capture an image. I do not get secure connection errors, or get mixed content notifications. There must have been something that survived the complete uninstall of Firefox, which reappeared when I reinstalled the program. The problems that I had appeared when I installed the update two versions ago.

I looked at "about:config" but found everything was set to default except those marked as "user set" which cannot be changed to a default setting because they require a number.

Do you mean with "they require a number"?

Integer prefs also have a default value and you can reset such a user set (bold) pref via the right-click context menu to the default value.

What integer prefs are you referring to that are bold?