win8.1 system, click on a window, "Currently active window" that window cannot be pinned

When two or more windows are displayed on the desktop at the same time, click on the next layer of the window, can not display, no matter how to click, or hidden behind the original top window, can only manually put the original top window after the minimum to see.
For example, a window is now pinned, b window in the back of a, exposing a part, I click on this part, a window border gray, b window border to blue, but the b window is still hidden behind a window, can only manually minimize a window, to see the b window, and then this time, is the b window pinned, next, I clicked the A window in the taskbar under the computer, the A window is also not top, or it appears under the b window, even though the border of the b window becomes gray.

win8.1 system, click on a window, "Currently active window" that window cannot be pinned