First off, let's define what hotlinking is. If you create a link within your web site in order to directly display another website's content (such as graphics, sounds, etc.), that's hotlinking. Note that hotlinking is not the simple placing of a URL link on your webpages. Rather, hotlinking adds content to your pages at the expense of someone else's web server bandwidth. One negative consequence of hotlinking is that the source file often disappears or is modified from the original format. This may result in a broken link on your site or could produce an odd-looking graphic on your page.
Hotlinking is acceptable if you have the permission of the host server who provides the content you wish to use. But without such authorization, hotlinking is highly unethical, if not illegal. If you are a web content creator or a web site owner, you need to know what preventative steps to take in thwarting others from hotlinking off your site without permission.
While there are various active techniques to prevent hotlinking on the server level, a properly written legal page is a good place to start. Adding a legal statement on your web site tells your visitors what restrictions you've placed on your web content. Something like the following line may be useful, where "the Company" stands for your organization:
Direct URLs to content in this site shall not be embedded and linked from within outside web sites (i.e., "Hotlinked") without prior written permission of the Company.
Unfortunately, some of your web visitors could care less about the rules you've established for your web site.
Put an end to unauthorized hotlinking with the .htaccess file. If your site is hosted on an Apache web server, and if your web space provider allows modifications to be made to the ".htaccess" file, you can add some very simple code that will protect your site content from off-site hotlinking. An excellent report on the subject can be found on this web page:
Here is another web page offering more details in layman's terms, written by a web space provider:
CGI scripts can prevent hotlinking. However, CGI scripts are marginally more difficult to set up than .htaccess. One example of an image protection CGI script can be found from this web page:
Not taking steps now to protect the content of your web site could result in higher fees from your host provider, caused by the increased bandwidth usage of hotlinkers.