I am new to ubuntu and I just installed it. when I tried to install git using "apt-get install git" I received error with "unable to connect". Then I found this question and did as what the question said. I installed git without any problem(I also installed vim and postgresql, no problem). But I received the following the error when I do "apt-get update".
W: GPG error: http://extras.ubuntu.com precise Release: The following signatures were invalid: BADSIG 16126D3A3E5C1192 Ubuntu Extras Archive Automatic Signing Key <email@example.com>
Then I replaced the sources.list with the original one--the previous one when I had problem using apt-get install. and the strange thing is that I can use apt-get install(all i did was just stop using the list file and used another one and then revert to the original one and the original one suddenly works for install) I still have the same error with update.
so what was wrong previously? why did I receive error now?