Firefox, Fluxbox, generic taskbar icon

[audiodef]

On my laptop, when Firefox downloads stuff, it puts an icon in my Fluxbox task bar to indicate the status of downloads. When everything is done, right-clicking on that icon brings up a dialog that says "all downloads complete".

This taskbar icon is a generic white document with a red "x". What iconset or use flag could I be missing that prevented this icon from being whatever it was intended to be?
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[ultraincognito]

I absolutely don't know what you must to do but on your site I would install the tango-icon-theme and look a result.
If you have a limit of the RAM but not the hard disk space you can install the Xfce. It entails some libraries. Probably the needed libraries.