This is an emulation of the Windows.Forms ComboBox. It is the combination of a
Textbox, with a DropDownList. For browsers with good script and css support, the
control will display as a normal ComboBox. For older browsers or those with poor
script or css support, the control will display as a pair of controls, one
TextBox and one DropDownList. Either way the serverside progmattic interface
will be the same.