You are here:  gunnars.net - Mozilla Help - Configuring Mozilla's privacy and security features

"When words become unclear, I shall focus with photographs. When images become inadequate, I shall be content with silence"   Ansel Adams


Another one of Mozilla's privacy and security features is image blocking with the help of the Image Manager. Mozilla allows you to selectively block images such as advertising banners.

Mozilla's Image Preferences


Above you can see Mozilla's image preferences.

• The recommended "Image Acceptance Policy" settings are:
  Select "Accept all images". You can also select "Accept images that come from the originating server" but this may lead to some sites being image-less. If you are e.g. on "www.cnn.com", the latter setting means that Mozilla will only accept images that are fetched from "www.cnn.com/...". If this site were to use a third party server to ensure that multimedia content such as images can be delivered even if the site is under high load, and many larger (news) sites do just that, this setting would also mean that the page you are viewing may be without images. So my recommendation is to allow all images and block them on a per-case basis.
• The recommended "Do not load remote images in Mail & Newsgroup Messages" setting is:
  Check "Do not load remote images in Mail & Newsgroup Messages". This is a very important and useful option (if you use Mozilla's mail client), which is often overlooked. It could save you from a lot of Spam.
  Now you are probably wondering, what images have to do with Spam. Simple: Many Spammers will send you Spam in HTML format. In the message, they are fetching an image from a server, often an "invisible" (1x1 pixel) gif, which has an ID added to it. This means that if the image is fetched from the Spammer's server, the server log will contain the ID that was assigned to your email address, letting the Spammer know that your address is valid and that you opened the message. This will, in turn, lead to even more Spam. If you have ever wondered about weird messages that did not seem to contain anything, now you know their purpose - to see, if you exist.
  So, I strongly recommend that you check this option, disabling the loading of external images in mail and newsgroup messages. If you are wondering if this will also make Mozilla not show you the images your brother or sister sent of the last family reunion, there is no need to worry. This option will not block images that are contained with the email, only those that are fetched from an external server.
  
• The recommended "Animated images should loop" setting is:
  The setting for this option depends on your personal preferences. Some sites use animated images. When used selectively, this can contribute to a more efficient use of available space on a web page by showing 2 different things in one place. However, too many animated gifs, especially when used by poorly designed advertising banner can be very annoying and add "noise" to the page. This will distract you from what's important, i.e. the page's content. So, if you visit pages that make you think you're in Vegas, I would recommend setting "Animated images should loop" to "Once", otherwise "As many times as the image specifies" will be fine.
  

Clicking on the "Manage Image Permissions" button will open Mozilla's Image Manager.

Mozilla's Image Manager


The Image Manager shows you sites that can and cannot load images. To remove a site from the list, simply click on the site's / server's name and then on the "Remove Site" button;

Selectively blocking images on a website:

If you have selected "Accept all images", you may want to selectively block annoying banner ads. To do that, right-click on an image and select "block images from this server"



Now, when doing that there is something to keep in mind: Mozilla will block the entire (sub)domain, i.e. if a site loads banner ads from "www.somesite.com/ads/", it means that Mozilla will no longer accept any image from "www.somesite.com", which most likely includes images that you want to see. If, on the other hand, the ad banners are fetched from "ads.somesite.com", or some other server like "ads.doublecklick.net", only ads will be blocked. So, if images seem to be missing from a site, simply right-click on where the image should be and select "Unblock images from this server".

Flash ads, advanced blocking:

As you could already see above, there are some limitations to Mozilla's "out-of-the-box" ad blocking capabilities. When ads are fetched from subdirectories rather than subdomains, blocking ads will also block all other images. In addition, an increasing number of sites use flash based ads, which cannot be blocked through Mozilla's preferences. Flash ads can have the negative effect of bogging down the browser and your entire PC (for those of us with older systems).

Fortunately, there are ways to greatly improve Mozilla's ad-blocking capabilities. If you install the AdBlock extension, the shortcomings mentioned above no longer apply. Now you can block subdirectories, specific types of ads (e.g. flash) and more.

---

Thoughts about blocking banner ads:
You probably find banner ads as "useful" as the next guy, so having the option to block them is a nice thing. Keep in mind, however, that running a website can be quite expensive, and the people working on the site like to be able to pay their bills just as much as you.  In many cases, a large part of a site's income will be through banner ads.

So, please use ad-blocking selectively. If you enjoy a site and they placed the banners in an intelligent (i.e. not obtrusive) manner, please don't block their ads.  I am sure they will appreciate it.

---

Previous Step. Introduction, Taming the Cookie Monster
Next step: Popup Windows.