In the WAPPage Editor, the code for each file (which may contain one or more cards) is automatically generated when the user switches between Design and Code view or Tree view or vice versa. Any errors found, will be displayed in the Output Window. The type of error, its description and its location within the code (line number and its position in the line) will be indicated. Only switching to code view in the design window and deleting the invalid code can remove the error.