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Block the Loading of Animated Gifs

I am trying to block gif's from loading, specifically animated gifs, but if that is not possible, then all gif's. The point is to reduce bandwidth. I am able to remove elements using .remove() and jQuery, but this still means they load. Is there a way to block the specific requests for the gifs so that they do not even load in the first place?
Edit: I am talking about making a Google Chrome extension

You will run into timing issues. If you use a content script you can remove those dom elements but since your extension activates when the page is fully loaded and ready, by then probably chrome already loaded them.
Small animated gifs dont consume much bandwith unless youre talking about the recent trend of making short videos with gifs. For those large ones you might prevent some frames from loading.

Preloading images in Firefox aren't being retrieved from the cache on the same page load

Some context, I am running a script on a website's home page to swap background images on a timer. We decided it would be better to attempt to implement preloading of the images, which prompts the following issue in Firefox:
Preloading images on the first page load will not prevent the browser from loading the image from the original source again instead of the cache. Oddly though, refreshing the page will successfully cause the image to be loaded in from the cache.
The JavaScript that runs on page load takes all of the image URLs, and attempts to preload them via calling (new Image()).src = 'http:// ...'; for each one.
Inspecting the page load revealed that the images would be loaded in on page load, but then the image would also be loaded in again when the slide was revealed.
Test Image Link (SO reputation restrictions): http://i.stack.imgur.com/E9KLM.png
In the image, the images -66.png, -21.png, -63.png, and -83.png were preloaded from the JavaScript, but are then requested again when the slider reveals that slide.
What's also strange is that the bottom images look like they were queued to be loading in since the page was created. Maybe it's because this takes priority over the script that was loaded once the document was ready?
To finish off, if I was to refresh the page and jump to a slide that was preloaded with the images, but never revealed, it is shown to be loaded from the cache like it should have been originally.
My theory is that the original background images are maybe declared to needing to be loaded from the server when the page is first loaded, but aren't actually loaded until the slide is revealed. On document ready, when the javascript preloads the images, they're not cached yet so they need to be loaded from the server. Then a slide is revealed and the browser tells that image that it needs to be loaded as originally declared.
Does anyone know why this situation is occuring? If so, are there any solutions to resolve?
I have an idea that involves adding the image URLs as a data-url attribute instead, and then having javascript preload them and add them as background images at that point, but I haven't tested this yet.

For those interested, we were not able to find a perfect solution for this.
What we did notice, however, is that the images were being pulled again based on their size. The larger the image size, the more likely the image was not fetched from the cache when the image was shown to the user.
We semi-resolved this issue by compressing our background images even further, and then greatly limiting the amount of images preloaded on the first page load. We found that these two steps greatly increased the changes of the images being pulled in through the cache when needed. It also saved more bandwidth and improved page loading times in general by a significant amount.

how to get a list src from img tag?

I'm building a webapp using sencha touch, and I need to use some images from another website. These images are updated every 10 minutes, so the source of the images is changing all the time. So I don't have an specific url where to get the images.
Can anyone suggest a way to get the source of the images using javascript?
I tried with jsonp, but got nothing more than an error.
I will appreciate your suggestions.

There is two javascript solutions:
Ajax request to the website API
Load the page into an hidden iframe, onload, fire the update of the image, search for the source image you want in the iframe childrens, then delete the DOM of the iframe

Does changing the src attribute of an image stop the image from downloading?

Let's say that I have two accordion tabs. The first one loads hundreds of images and is open when the page loads.
I want to be able to stop the images from downloading if the user clicks on the second accordion tab. Will changing the src attributes of the images via js stop the images from downloading? Or do the requests just continue until completion and not show up on the page?

I have a script that loads the SO logo in exactly 3 seconds that I had made for another question.
http://alexturpin.net/slowimage/slowimage.php
Using it, I tried to reproduce the problem:
var img = new Image();
img.onload = function() {
alert("loaded");
};
img.src ="http://alexturpin.net/slowimage/slowimage.php";
setTimeout(function() {
img.src = "";
}, 1000);
http://jsfiddle.net/Xeon06/RrUvd/1/
From what I gather, in Chrome, the onload doesn't get fired, but the browser keeps on showing a spinner and if I go on the network tab and find my image and check it's content, it's there. So my answer would be no, the image still loads, at least in Chrome.
This is an interesting problem, I suggest you try and test it in as many browsers as possible and write some kind of blog post on it.

Your browser asks for that image with a specific HTTP GET request, as
specificated in HTTP protocol. Once it asks for it, the http server
starts the transfer.
So, it is between the browser (as http client) and the http server.
Since http protocol does not takes into account the option to abort a
transfer, the browser should implement a out-of-standard mechanism to
programmatically abort the connection. But since this is not specified
in any standard, i think you won't find any way to do that with
javascript or any client side code.
You can try window.stop() to stop all requests, but not individual
ones.
If you wanted to stop a single request for a large image, what you
could do is load the image into a document within a hidden IFRAME. The
onload event of the IFRAME can be used to load the image into the main
document, by which time it ought to be cached (presuming you have the
caching directives configured to do so).
If the image is taking too long, then you can access the IFRAME's
contentWindow and issue a stop command to that.
You need to have as many IFRAME elements as there are images that can
be requested simultaneously.
Taken directly from here & here.

Not sure if it will, just like the other comments. But I can suggest am approach that will work well. Assuming not all the images are visible, just set the right src attribute when they become visible.
So default the url to myGray.gif when it is not visible and set it to myImage.jpg when it does come into view.
When you close the current accordion, you can set the image source back to your lightweight gif again. (this prevents a bug related with gc on some versions of the ipad).

What's the best way to make external images and JS files to not affect page load time?

On a lot of the pages I work with there are a lot of external(non-critical) external images and js files that get called that affect the load time. One of these is a tracking pixel for an ad company that sometimes can take a few seconds to load and you can see this hanging in the browser so it gives a poor user experience. Is there a way that I can load these and not have them count as the initial page load? I've seen similar things that launch a timer and once the timer fires they load but I'm worried that if the user leaves the page too quickly the tracking pixel wont have time to load.

Not really - the point of tracking using a gif is to track users regardless of whether they have javascript or not. Delaying the load of the gif would require javascript, so would defeat the point and potentially mess up your stats.
The best method is to put these 'unnecessary for page load' things at the end of the code, inside the closing body tag.

If you can load the tracking pixel further down on the webpage, preferably as close to the end BODY tag as possible, it will likely process all other content prior to that image first, making the page load appear to occur faster in the event the image isn't loading very fast.
This can be explained (if taken slightly out of context) by Yahoo YSlow's "Best Practices for Speeding up your Website" section on put scripts at the bottom.