Try this eccentric situation. Take someone with a photographic memory and show them your "copy protected" page. No highlighting will be done but the person with the photographic memory has already stolen your page. It's not possible to have content that can be viewed in a browser, but not copied. By the time it's been viewed in a browser, it's already been copied because you have to download a webpage to view it in a browser.
I wrote a little rant on it at http://fourisland.com/blog/and-like-magic-nothing-happens/ if you want more information about this.