This test is only relevant on platforms where dragging over taskbar buttons will switch between applications.
Ensure that at least one other application is open and visible on the taskbar. Maximise this browser window. Select this text. Drag the selection downwards, over a blank part of the system taskbar, and release the drag. Drag the selection again, over the taskbar button for the other application (without passing over any other buttons on the taskbar). Fail if the drag placeholder does not appear when dragging the selection. Pass if the other application becomes focused.
Repeat this test while dropping on other parts of the taskbar, such as:
WARNING: different operating system versions handle this differently - Windows XP Taskbar in particular can cause several more problems than the Windows 7 Taskbar