Insert image using the image button on the uploader toolbar.

When you have uploaded the image resize it to 200 pixels wide.

Insert the smaller file into the url section of the image uploader. Fill in the alternative text for the image.

In the link tab, the url should be set to the original, full sized image stored on the server. Do not set a target.

In the advanced tab, set the id and stylesheet classes each to ‘caption’. Set the long description and advisory title fields to the caption of the image.

When the content has been saved, the smaller image should be shown. When you click on it, then the larger image should be shown.