Remove a tag in Facebook's standard image viewer.
- Look below the picture and to the right of the comment section.
- Click the "Report/Remove Tag" link.
- In the dialog box that appears, check the "I want to untag myself" checkbox.
- Click the "Remove Tag" button that appears.
- Point the cursor at the bottom of the image and click "Options".
- Click the "Report/Remove Tag" menu item.
- Perform steps 3 and 4 shown above.