If you don't want the image to be clickable, click the 'None' button and it will get rid of whatever link (in this example, www.google.com) is in the link address box.
If you want to specify a link to another page, type it in the address box where I currently have www.google.com typed.
If you want to link to a page which contains only the image (in full size), click the 'Link to Image' button.
If you change your mind, and want to put the image link back to the way it was, click the 'Current Link' button or the 'Cancel' button. Keep in mind, though, that clicking 'Cancel' will also undo any other changes you made on the edit image page since last saving.

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