In reality there is no SURE FIRE way to stop folks from taking or linking to your images,
but there are a few ways to discourage image hijacking.
One of my favorites is to just be sneaky. Of the sneakies one I like is to have
two DIV's positioned to the same location but having different z-indexes.
The lower z-index DIV has your image of desire, while the upper z-index DIV has
a transparent pixel sized to occupy the same amount of space as the "protected" image.
The hijacker saves this image named "034563.gif" or some such thing (to keep being sneaky) and
not give away the sneaky with something obvious like "pixel.gif"
By just quietly frustrating the thief, in most cases they'll just scratch their head and go away.
CGI , but in most cases a nice simple sneaky is all thats really needed to discourage
the average hijacker. with the more advanced hijacker being not worth the effort, as
if nothing else they could just press their [print screen] button to
copy an image of the screen to the clipboard and use their image editor to crop out the