One thing is certain in project management—change. If you're being a good project manager, expect lots of changes to the schedule. You need a tool to help you keep track of changes and to give you back control of your schedule.
Welcome to Task Drivers.
In Project 2007, select a task. On the Project menu, click Task Drivers.
In the left view, you'll see detailed information about the selected task on the right. You'll see the most critical factors that affect the scheduling of the task, such as date and task relationship information.
Another Tip You can click other tasks without closing the Task Drivers pane. The Task Drivers pane always displays the scheduling drivers for whatever task is selected.
Where is the task drivers button in 2010?
In Project 2010 it is now called Task Inspector since it does more than just tell you why your task is starting when it is. The command is located on the Task Tab - Task group and is called Inspect.