How do they set all black in the background

I used to watch videos of poker players. And I see that the background of their desktop is black. how do they do this?

Right click on background -> Personalize -> Desktop Background

Then select an image of black or whatever you want

Heh, just yesterday I accidentally right clicked on another website + saved the background which made my desktop all black. I didn't know could do that before, so then I changed it to Cardschat's background, nice soothing color.

where should I right click?

On the desktop... the click properties.

Depends on the site.

But you should be able to choose View Avatars. It should also give you an option nearby to remove the players and use only a black screen.

Personally, I like the colours....