I guess you know you can run your browser in full screen mode using the F11 shortcut key. Windows Explorer also supports this feature.
Running in full screen, where an application UI covers the entire screen, over the TaskBar and any Desktop/Tool bars, is handy when a user has a limited screen size (laptops) or when you just want more to be visible by the browser or the Windows Explorer.
Running your application in full screen might also be handy if your users want to be focused only on your application’s window.
Looking for the best approach to change the background color (and other properties) of the focused data entry control in a Delphi (VCL) application?
By (Windows) design, the control on a data entry form which has the input focus is not drawn (/highlighted) differently from other controls (i.e. those without the input focus). In case of the TEdit (or TMemo and alike) control, only the blinking insertion point is displayed.
To provide visually more attractive user-friendly interfaces for your Delphi applications, you could decide to change the background color (and maybe some other properties) of the currently selected control – the one that has the input focus. Of course, this would include restoring to the original background color when the focus shifts to another control.