Ever heard of hotlink protection? If you have a site with a lot of photos, you’ve probably been hotlinked without even knowing it. Hotlinking is when a website embeds an image tag in their HTML that loads an image from a second site rather than storing the image on their own servers and loading it from there. If a site hotlinks it doesn’t have to pay for the disk used to store that image and the bandwidth that is consumed when web browsers load the image. If you have a very popular web page and you hotlink images from someone else’s server you can cost them a lot of money.
Many sites use a technique called hotlink protection to prevent other websites from hotlinking their images. Hotlink protection detects if another website is loading an image you host and prevents the image from loading. There are reports that if you use hotlink protection, Google may remove you from their image search results. The reports are spotty and some webmasters who have protection in place are not reporting a problem yet, so keep an eye on this issue if it applies to you.