This is a critical part of every website project, especially ones that include extensive functionality. Project managers play an important role in a variety of ways such as specifying: goals, requirements, schedule, budget and the Project Planning. They also often are responsible for completing Definition deliverables such as sitemaps, wireframes, and functional specifications as well as QA and testing.
The amount of project management time needed is typically 20% of the total project time e.g. if the project has 100 hours then 20 hours should be allocated for project management.
Insufficient allocation of time for project management increases the risk the project will not run smoothly or encounter cost overruns.