Secondary Windows in Online Help - What Do Users Really Make of Them?
STC Usability Newsletter: "In conducting these two tests, Digitext set out to investigate how the discretionary use of secondary windows might contribute to the overall goal of easy-to-use Help systems. The overall conclusion is that there is little reason to assign specific types of topic to different secondary windows. However, it can be helpful to use a secondary window for a link to a sub-procedure or layer of additional detail, as long as the current window remains visible on screen when the new window appears. In this case, the two windows show a valid relationship between the two topics, and the user is able easily to return to the main topic after completing the sub-procedure." (2001-04-29)
The link address is: http://www.stcsig.org/usability/newsletter/0101-secondary-windows.html