Resolving violations
A violation is some kind of problem with the project, such as an impossible dependency loop, a task which starts before the project start date, or a task which is outside its start or end constraints. When a task has such a problem, the violation symbol 
appears in the Violations column of the task outline.
appears in the Violations column of the task outline. You can click the little violation symbol, or the Violations button 
in the toolbar, to open the Violations window. 
in the toolbar, to open the Violations window. This window lists all of the violations in the project. Most violation explanations include links you can click to immediately resolve the problem.