This is a requested popup. But it is coded in a way that it will try to create an UNRequested popup once it is itself created. If you have set your browser to suppress UNRequested popups, then you will not see the popup and you may see an icon image at right-most side of your status bar (depending on your setting).
You should see this very window in Firefox whatever your window popup control setting is because this window is the result of you clicking a link which calls a function creating this window.
If you reload this page, it will then try to re-create again the UNRequested popup.
Try this: close the UNRequested popup window and then press F5 or the or Ctrl+R and the window will be reloaded but the UNRequested popup will also be re-created if your setting allows UNRequested popups.