sys_icon_online icon location.

I have just installed 7.1.3. I want to change the image for sys_icon_online but I can't find the image anywhere. I tried firebug, but it only shows me the .CSS style and not the image location. I understand that this is a stupid request, but it's really getting under my skin for some reason. I have looked everywhere I can think it might be.

Thank you!

Okay then, It's not an image any more. It is just a CSS style in common.css producing the image.
I just needed to walk away for a few minutes, too many hours staring at it will drive a guy batty.

It may have been switched to using the FontAwesome font for the icon.  If so, then you can switch it to use an image instead of the font.