border="0" cellspacing="0" cellpadding="0">
Of course, you must substitute the URL of your image for MYIMAGEFILE and the width and height of your image, in pixels, for WIDTHOFMYIMAGE and HEIGHTOFMYIMAGE. Also, transparent.gif must be a completely transparent GIF image, one pixel by one pixel in size. You can make a transparent GIF image using any quality graphics program. For more information, see the image formats entry.
This trick works by displaying your actual image as the background of a table, and displaying a scaled-up transparent image as the content of the table. The user, of course, sees your real image "shining through" the completely transparent GIF; but when the user right-clicks on the image to save it, they get the 1x1 pixel transparent GIF instead of your image.
In short, there is no perfect solution; the best you can do is slow users down a bit using the table background trick.
You should, however, consider "watermarking" your images; add an unobtrusive but recognizable mark to the image itself, so that you can later prove that the image was stolen. You can add a mark that is obvious but not unpleasant to the user, or you can use more sophisticated software that does not leave a visible mark. Tools in this area are available from Digimarc and from ReaWatermark.
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