An image placeholder does not display an image in a browser. Before you publish your site you should replace any image placeholders you’ve added with web-friendly image files, such as GIFs or JPEGs.
If you have Fireworks, you can create a new graphic from the Dreamweaver image placeholder. The new image is set to the same size as the placeholder image. You can edit the image, then replace it in Dreamweaver.
Double-click the image placeholder.
Click the image placeholder to select it; then in the Property inspector (Window > Properties), click the folder icon next to the Src text box.