Please don't take this the wrong way, this question comes up fairly often here and when the proper advice is given the OP normally gets upset.
Disabling right clicks is bad and will at best provide a completely false sense of 'security' for your client.
How clever will you look to your client when you install this thing then he sees his content somewhere else?
Far better to educate your client than to obfuscate the issue by seemingly to meet his demands. Tell him that what he wants is not a practical solution to what, for him, is a real problem.
Whilst 123HTML Protector and scripts of its ilk may provide (extremely) casual 'protection' for the content you must be aware it won't really protect much at all.
I assume you have educated your client in how the web works and by publishing something online you give the world the option to copy it. They will if they want to, you can't stop them by disabling right clicks.
It's the same as with a printed brochure really. Does your client have one? Does he employ a fiendish device to stop people photocopying or even photographing its contents? Probably not.
Obviously I don't know what this content is, but is it really that amazing and unique that it will be a problem if it is copied? I'd be suprised. If it is something very special that will create problems for your client should it be copied then the best advice is to not put it online in a useable form.
If security and breach of copyright is that serious an issue for you client then he/you should consider other means of protection. For example, if he is wanting to protect images (I guess this is the case) a much more sensible option might be to watermark them in some way.
Disabling the right click action is, at best, pointless and at worst irritating.
Finally, if this content is a Flash movie, the right click brings up the Flash Player context menu anyway.
I hope that is of some help for you in getting a better understanding of why 'we' all give the same advice. i.e. Don't bother with it.
Would you care to show us the site in question?
<honk>*:O)</honk>
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