Complex sentence: It is important to note that "Web 1.0" has been retroactively named only after the introduction of the term "Web 2.0", and has very loosely defined boundaries.
Split into simpler sentences: It is important to note that "Web 1.0" is a retronym. That is to say that it has been retroactively named only after the introduction of the term "Web 2.0", and has very loosely defined boundaries.