A post whose source is a direct link to a Tumblr image, rather than to the Tumblr post containing the image. These are considered bad links because there's often no way to find the original Tumblr post from the image link. If the original tumblr post has not been deleted, the original source can be found manually through the direct link.
If you see this warning while uploading, it means you should paste the link to the Tumblr post on the upload page, not the image itself.
