YOUR BEST BET IS TO GET THE ADVICE OF AN ATTORNEY, BUT WHEN YOU PUBLISH SOMETHING AS IS ON THE INTERNET IT IS AUTOMATICALLY COPYRIGHTED. BUT REGISTERING THE COPYRIGHT IS DEFINITELY IA GOOD A IDEA TO PROTECT THAT COPYRIGHT.

http://www.copyright.gov/
Why should I register my work if copyright protection is automatic?
Registration is recommended for a number of reasons. Many choose to register their works because they wish to have the facts of their copyright on the public record and have a certificate of registration. Registered works may be eligible for statutory damages and attorney's fees in successful litigation. Finally, if registration occurs within 5 years of publication, it is considered prima facie evidence in a court of law. See Circular 1, Copyright Basics, section “Copyright Registration” and Circular 38b, Highlights of Copyright Amendments Contained in the Uruguay Round Agreements Act (URAA), on non-U.S. works.

If your client doesn't want it, your client doesn't want it. Just make sure you save the email in which your client said they didn't want it.

Really, it doesn't matter.

It is NOT necessary.

It is only to let those viewing your site be aware of your legal ownership over the work -- it is more of a public declaration than anything else. It can be helpful or even smart to have -- it may even help protect you slightly in a legal dispute, but it is not necessary or required by any means -- your work is your work regardless if a notice is placed.

This is true in the United States primarily. We are one of just a few countries that act under the "first to use" policy -- the first to use a work is the owner of the work. The copyright with year tells the public when you say you started using your work.