Non functional arrows in white boxes

I have three white rectangles with an arrow down in each that are about 1/2"x 1/8". The arrow cannot be clicked, the box cannot be moved. One is on the laptop and two are on the external monitor. They are making me crazy. Any ideas? I have seen similar questions and the response seems to be that they just go away. Mine are not. I use a MacBook air and an external monitor.