The problems view displays errors and warnings (problem markers) that exists in yours projects. You can double click an error or warning in the view to open the associated editor.
In the process editor process elements that have errors are marked with an error overlay icon.
Window > Show View > Problems
This view is a standard Eclipse IDE view. More information about the Problems View can be found in the Online Help: Workbench User Guide > Reference > User interface information > Views and editors > Problems View.