If all the above criteria are satisfied then copyright will vest in the work. These rights can be varied in some cases by agreement or by the courts. For most works which will concern users on the Web the period of protection will be the life of the author plus an additional 50 years. If you have several authors, it is when the last one dies. Currently there are moves to increase the term of protection to the life of the author plus 70 years.
Infringement is always a matter for the courts to decide.
There are a million little rules and exponentially more exceptions to those rules. Direct infringement Where someone has copied the whole work exactly infringement will be obvious. The test is easy to state and yet hard to apply. The inference will be stronger the greater the degree of similarity. The main issue that you need to be aware of here is that of parallel importation.