While much of the software that people depend on is written by professional software engineers, increasingly, important applications are being created by non-professional (end-user) programmers. Using tools such as spreadsheet environments and web authoring tools, these programmers are creating software that is being used to support significant activities and inform decisions. Such software needs to work dependably and increase user productivity, but evidence shows that it frequently does not. For example, studies have shown that a large percentage of the spreadsheets created by end-users contain faults, and data suggests that time spent maintaining web macros may actually impede their users? overall efforts.