Firefox provides option for disabling the automatic loading of images. By default this feature is enabled in Firefox. If you are interested only in textual content of a web page then you can disable this option to speed up the loading of a web page. The can be disabled using the Firefox options menu.
Click Tools –> Options menu and navigate to content tab.
Un mark the check box with label as Load images automatically. This would disable the automatic loading of images in Firefox. If you want add any exception to this then you can click the Exception button.
Enter the web site details in Address of web site text box and click the Allow button.
Any websites added to this list will have the automatic image loading feature enabled.