I just installed free60 on my xbox 360 and when I try to browse, it says "Cannot communicate securely with peer" I tried to update Firefox with sudo apt-get update and sudo apt-get upgrade but both didn't work. Any way to fix?
The problem you have with Linux on the Xbox 360 is any usable distribution out there is over 10 years old and no longer supported. Modern versions of Firefox also no longer supports PowerPC processors, which is what the Xbox 360 has. Any websites that are plain old http should still work to some degree on the browser you have now, however any site using https will not work as the browser will not know what to do with modern SSL certificates. Perhaps you will have some luck with SeaLion - A web browser for 32-bit PowerPC Linux if you can get that installed.
At a guess you'd extract it and run the script "run-monzilla.sh" - any Linux port to the 360 is obsolete though as mentioned, so I very much doubt it will work as it seems to require modern versions of Debian Linux. You might however get better advice from more experienced Linux users on the site hosting SeaLion.