Preloading image is not just for rollovers, you may want to preload an image that will load on a page to reduce the wait time for your users. You may also want to preload images that are in layers that are hidden.
Preloading an Image
1. In the behaviors panel, select a browser version 4 and above.
3. In the document window, select the body tag.
4. In the Behaviors Panel select the Preload Images action.
4. In the dialog box that follows, enter the name/path of the image you want to preload. For every image you want to preload, add the "+" button. Click o.k when done.
5. In the Behaviors Panel select an onLoad from the events list if it is not already selected.