Tri-state checkboxes are used to indicate that some, but not all items in a list have been selected. As with a typical checkbox, it is displayed as checked when all items are selected and unchecked when nothing is selected, but the third state does not look the same in all interfaces. A tri-state checkbox is one of those controls that still doesn’t have a clear standard. I think there are three reasons for this: They aren’t needed very often. What has been used in the past doesn’t work very well and so designers keep trying to come up with something that works better. Rather than solving the problem, some designers simply avoid it. DIFFERING IMPLEMENTATIONS Figures 1, 2, 3, and 4 show four unique implementations of tri-state checkbox displays. Figure 1 is a screenshot from Yahoo!® Developer … Read entire article »