So, I've seen a lot of art that is hotlinked and I bet some people don't know what is it, therefore here you have an explanation:
Hotlinking is direct linking to a web site's files (images, video, etc.).
This uses that page bandwith. Bandwidth refers to the amount of data transferred from a web site to a user's computer. When you view a web page, you are using that site's bandwidth to display the files. Since web hosts charge based on the amount of data transferred, bandwidth is an issue. If a site is over its monthly bandwidth, it's billed for the extra data or taken offline.
In lots of sites it is considered theft.
With this explained, I would like to remind you that to avoid this simply upload your picture in image host sites such as tinypic, imageshack...
It will save up lots of trouble to you guys, as some sites that know their images are being hotlinked, ban people for this.
Commonly Used Image Hosts: (added by Vennenum)
* - requires registration