Thankyou all.
Very helpful as ever.
Another more devious trick, is to use overlaid layers, with a
transparent GIF guarding the original image, which you also split into
sections - and watermark prominently.
The basic fact, if you display an image, it can be stolen - scripts
can be jammed by script-blockers, and view source can then be used to
probe for other obfuscation.
Flash and shockwave can probably be decompiled, and there's no
stopping a screengrab.
Other than stamping them, displaying a copyright notice and not using
any images that have monetary or other value, there's not a lot you
can do. Also sizing an image to 1/4 area and then using width/height
to resize can look just about ok, but makes further enlargement
unrewarding.
So - appeal to people to respect your rights, make ripping off your
images difficult, and make the result obtainable by doing so as
minimal as possible, and as time-consuming as possible.