Are you concerned about other web sites calling images on their web pages to image files that are actually located on your site, and how it affects your bandwidth?

Hotlink protection is a feature located in your control panel to block any site making an image call that doesn't come from your site itself, or from a list of sites you allow access to. 

This can also be done by editing the .htaccess file used to control these rules via shell access, FTP access, the Filemanager, or the "Edit .htaccess file" feature in your control panel. However, the hotlink protection feature offers the most simple and straight forward interface for those not familiar with the proper syntax and directives in the .htaccess file itself. 

While using the Hotlink protection feature in the control panel, you can create a list of allowed domains, IPs or specific URL addresses that are allowed to load images from your site. 

Hotlink protection can be enabled or disabled and should automatically determine what domains/addresses are allowed to load images. Also, please note that anytime you add a new sub domain or pointed domain to your account, these rules will affect it. 

Hotlink protection works by checking the 'referer' field (this is intentionally spelled referer with one 'r') that browser's carry when they access a web site and make a call to a file--this is the field that tells you where the browser is coming from when a file on your web site is accessed. 

Some browsers do not carry the referer field, but few browsers that old are still in use. Other conditions apply as well where the referer field may not exist. For example, if someone accesses your site from a bookmark or if they type in the URL in their location (or "Go") bar on their browser the referer will not be carried.  While this isn't perfect technology, it can help to deter some people from calling your files on their site and use your bandwidth. You can then refuse access to the image file, or you can display a default image with a message, such as "Images can only be called from my site".