The copyright page is located at the beginning of a book, manuscript or other work before the title page. If a copyright page is removed from a book or does not contain the proper information, that does not mean that the work is not protected under copyright law.
With access to the Internet, libraries, cell phones and other forms of communication, you may be nervous about exposing your work. However, your work is protected almost instantly. The U.S. Copyright Office website notes that "your work is under copyright protection the moment it is created and fixed in a tangible form that it is perceptible either directly or with the aid of a machine or device."
All copyright pages have the same general information listed. The Book Designer website notes that three things must appear on a copyright page: the © symbol, the word "Copyright" or abbreviation "Copr."; the year of the first publication of the work; and "identification of the owner of the copyright---by name, abbreviation or some other way that it's generally known."
Reproducing copyrighted content without proper permission from the copyright owner is called copyright infringement. Copyright infringement can result in legal fees or other consequences. However, the "fair use" exception allows you to use some parts of the copyrighted material without the copyright owner's permission. The Stanford University Copyright and Fair Use website notes that quoting lines from a song, using an excerpt from a magazine or newspaper or quoting a medical journal are instances where you may be able to use someone else's work without direct copyright permission. The main concern with fair use is that there is no defined rules for the policy, so, if the copyright owner disagrees with your using a portion of the work, you could run into legal trouble. If you are unsure if your use will be considered copyright infringement, write to the copyright owner (noting how you wish to use the piece) and request permission to reprint that portion of the work.
When a work is no longer protected by a copyright, it can used by anyone. This is called "public domain." A University of North Carolina website notes that a work can enter into the public domain when "the copyright has expired, the author failed to satisfy statutory formalities to perfect the copyright, or the work is a work of the U.S. government." Once a work is part of the public domain, you do not need to request permission to reuse the work; however, you should still give credit to the author and title of the work.