It means ya posted a direct link to the picture instead of copying it and posting it from your own server.
When you hot link to other peoples photos, every time somebody loads the photo to look at it, ,no matter where it is on the web, it costs the original person money in bandwidth expenses.
If too many people look at the photo, the person who originally put it on the web can have their web service cut off for the rest of the month if the amount of downloads goes over their allotted amount.