I don't think there is any way for you to control that... Your best bet is to NOT post high res images online if that is a concern for you. Never post anything larger than 640x480 and keep the size of the file to a minimum...
John's advice is definitely the best and I'll just add that if you absolutely must post high res images for clients or others to see specific detail for a purchasing decision or evaluation that you make use of your image editor's watermarking feature or create you own "watermarks" from semi-transparent layers atop the image which you can add your name and copyright info to.
You can get java scripts that stop people being able to right click and save as, but then all they need to do is press the print screen button, and they have the image on their clipboard anyway.
Thanks for the tips, folks. I really do appreciate it very much.
I'm new to this group and I'm really loving it. I've had some great ideas in the past couple of days and I hope I got some great shots (I think they're great, but I'm biased LOL).
If you wanted to go through the trouble you could also place the image in a table with a transparent gif image covering it so that when you right click and save the image you're actually only saving the gif.
You can get java scripts that stop people being able to right click and save as, but then all they need to do is press the print screen button, and they have the image on their clipboard anyway.
Doesn't this capture the image at screen resolution only?
If you are posting a comp for a client, you can put a big copyright notice right across it, or a big "FPO" (for position only) as is traditionally done for mechanical comps.
If you have your own website (as opposed to an account at a photo gallery site like pBase) it is unlikely anyone will "browse" accross your images to steal them anyway -- just give the client the direct URL. You can even protect folders with passwords so people can't access them.
Please note that if someone were to steal your photo for commercial use, you will need to have actually registered it with the Library of Congress Copyright Office before you can sue them for damages. Almost all the documents and forms you need are there, mostly in PDF format for easy downloading.