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I was checking my gmail for the first time on Firefox in Ubuntu 12.10 and a message popped up asking something like, do I want to install the gmail app? I clicked yes and it put a letter icon into the top right of my screen, I guess what you call the tray.
Anyway it turns out this app is completely useless and I now want to remove it, but I cant! I've looked under "Installed" within the Ubuntu software centre but it isn't there.