Similarly, you can specify colours with great accuracy, and see exactly how they appear on your own screen (which may be fully calibrated and colour managed), but this tells you little or nothing about how those colour will appear on a user’s monitor. Differences between the standard set-ups of the Mac and PCs mean that the same image will tend to vary in ‘gramma’ (midtone balance) between platforms, and the differences between individual machines can be just as significant. Testing your designs on several different computers, as well as in different browsers, is a good way to ensure any potential problems are within acceptable bounds.