[Typo3] image links do not work?

[Bing Du]

When I edited a content element, I clicked 'Image Links' and then 
entered the url of the image (e.g. http://www.my.edu/images/one.jpg), 
checked the 'Chick-enlarge' box, then saved the content element. 
However the image does not show up on the page.  I can see the link 
being inserted into the image_link column in the tt_content table fine. 
  The image link itself can bring up the image fine in the browser.

What did I miss?

Thanks in advance for any help,

Bing