A cPanel functionality, known as HotLink protection prevents other websites from directly linking to files on your website. This means that when another website is visited, it cannot load pictures from your pages - this is one of the ways for limiting the outbound Traffic for your account.
An example of hotlinking would be a different website using HTML code to display an image from your site. In effect, the other website is using up your Bandwidth quota.
Please click on the HotLink Protection icon in the cPanel's main page and follow the instructions. Include the websites you wish to have access to your files - those may be affiliates or friends, linking to your banners, etc.
In order to allow certain file types to be accessed, please enter their extensions in the space provided - this way you can allow other websites to reach for your images, but disallow video or audio files from being accessed.
cPanel attempts to add all the domain names that you own to the allowed list, still if you have accounts on other servers you may need to have some of those added manually.
Make sure that you include all sites that need to access your protected files in the first bank field or they will not be able to view the files. If you still cannot view a file, try disabling Hotlink Protection to see if it is the cause of the problem.