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

• 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 link 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.

Make sure that you do not block (third-party) images, the permissions.default.image pref on the about:config page should be 1.

Make sure that you haven't enabled a High Contrast theme in the Windows/Mac Accessibility settings.

Make sure that you allow pages to choose their own colors.

• Tools > Options > Content : Fonts & Colors > Colors : [X] "Allow pages to choose their own colors, instead of my selections above"

Note that these settings affect background images.

See also:

• http://kb.mozillazine.org/Website_colors_are_wrong

There are extensions like Adblock Plus (Firefox/Tools > Add-ons > Extensions) and security software (firewall, anti-virus) that can block images and other content.

See also:

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes
• http://kb.mozillazine.org/Images_or_animations_do_not_load
• http://kb.mozillazine.org/Websites_look_wrong

Did you just start having this problem in the past 48 hours with the update to Firefox 38, or were you having issues with Tumblr in earlier versions of Firefox?

This site looks fine to me in Fx38 (Windows 7 x 64 like you), so hopefully we'll figure out the issue with your Firefox: http://www.scarygoround.com/?date=20150406

It was both recently (38.01) and more long-standing. I'm sorry I don't have an exact date for the start of this problem but it is more than a week ago.

Does this page look good to you? It should have about twenty-five images of waterfalls on it. After two minutes of loading, precisely one image appeared in Firefox. I think you have a problem:

https://www.tumblr.com/tagged/waterfalls

I'm spoiled at the office, since the page loads all 22MB in about 11 seconds (according to the Network Monitor section of Firefox's Web Console -- screen shot attached). I'm sure on a normal connection it takes at least a minute to download that much data.

I'm using the NoScript extension, so some scripts that might conceivably slow down the page are blocked from loading, including scripts from Cedexis Radar, Scorecard Research, and Google Analytics.

If the suggestions in cor-el's reply do not help, could you test in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any difference?

The Net monitor acts a bit weird. The throbber on the tab stops after about 4 seconds, but the Net monitor suddenly starts to reload the page to load a lot of data (177 requests, 23,098.35 KB, 22.26 s) (Ctrl+F5).

If I select images then this shows: 126 requests, 18,428.92 KB, 20.04 s

This response butters no parsnips. There's no explanation of the problem, and certainly no useful suggestions so far. Reloading the page doesn't help; at best, a different image loads in lieu of all the others. The problem is not with permissions, nor is it a Javascript issue. Firefox 38.0.1 is simply not loading images from multiple sources and I have no explanation why. This is a fairly severe problem, and no one at Support seems to know what do do about it. I am not pleased with the responses so far. Not a passing grade in my outfit. What's the next step?

progan01 said

Mozilla has already admitted a memory leak keeps images from appearing from multiple sources. Well, if I have Tumblr open, not all the images there display. Some simply lead to links saying 'Access Denied' and some simply don't even have a URL attached to them; there's no indication an image is there at all. The more Tumblr windows I have open, the worse the problem, and the longer each page takes to load. These problems do not occur on Internet Explorer 11 at the same time, looking at the same pages. Images load and display and, where an image is not available, a broken-link icon appears. Something is very wrong with image handling in Firefox 38, a problem so grave that it threatens the usability of the program. When I can't get the images for the books at John Allison's "Scary Go Round" page but they appear instantly in IE, then there's a fairly severe problem here not adequately addressed. I think you need to look into this, and quickly. As it stands, Firefox is broken, for all practical purposes. It is not usable for any Web page with multiple images.

All right -- that suggestion allowed me to do some troubleshooting. It seems HTTPS Everywhere is filtering out all sites that cannot be forced to use a secure connection when reached by Firefox. This provides an answer but not really a solution; I cannot use Firefox for accessing pages with multiple images, secure or not, because the contents will not be displayed fully. I am grateful to have this knowledge, but it seems I can't be secure looking at multiple-image pages, or else have to do without the images. Not what I hoped for, but I'll take it.

Does HTTPS Everywhere have a way to make exceptions for images, or exceptions for particular sites? While it is ideal not to have any insecure content in a secure page, even images, this is only Tumblr and not a transactional or healthcare site, so if data "leaks" from the page, it doesn't seem that it would have a huge impact on you.

HTTPS Everywhere does not make site-by-site exceptions, unlike NoScript which can be tailored to allow certain Javascript operations but not others. The concept was to force the site to transmit data in secure form, which is a good idea generally, but not all image encryption schemas are compatible with HTTPS and so these images can't be received.

If we could say which sites were secure and which unsecure, such programs would not be necessary. A good many crackers use innocuous sites as infection points, and since the development of steganographic coding, images are by no means invulnerable to being turned into vectors for attacks, carrying malicious code inside, say, that image of Batman or Emma Watson. Or waterfalls. I am not the one who can determine which site, which file, which line of code downloaded in the background will have a huge and unfortunate impact upon me. Therefore I defend against them all.

'Mithridates, he died old.'

I understand the appeal of HTTPS for privacy, since it prevents eavesdropping on the content of your requests, but I don't see that it helps with preventing attacks: if the attacker can get the image into a trusted site, he probably can host it on a secure server.

HTTPS is not the end-all of security; it is notably weaker than European standards and prone to attacks using spoofed security certificates. Nonetheless I'd rather have it than not, because it helps to keep the number of dumb attacks down.

I note in passing that the real worry here is not local penetration of my machine, but infiltration of the servers and their control systems by such means. For the last four months, at least, I've been watching the incidence of DNS poisoning go up sharply. A good many sites, some of them generally acknowledged as 'trusted,' are being spoofed and their traffic redirected. Attacks are getting through by many means, and not to individual machines but entire networks. It's a lot easier to mount a man-in-the-middle attack when you control the DNS tables between a bank and a customer. You could say it becomes an industrial operation.

We are all vulnerable, and the tools we use are not as recent or as capable as the tools the criminals use. It behooves us all to do what we can to protect ourselves, and to be wary of unguarded or unsuspected content. There is in fact no reason to trust any source unconditionally. Those who do, or who think they don't need to be so protective of their access, are very much in danger of having their ID, their access and their connections compromised by unknown parties. You are not safe, whatever you think.