how to set up nectwork proxy for update ubuntu

[psudheera]

hi friends, I have this problem that I can't set up my university proxy settings to update ubuntu. I can access internet through it. I set the proxy setting under the network but still update fails. Can anyone help me. thanks.

I'm getting this error :

W:Failed to fetch http://ppa.launchpad.net/cscarney/unity-web-place/ubuntu/dists/quantal/main/source/Sources  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/cscarney/unity-web-place/ubuntu/dists/quantal/main/binary-amd64/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/cscarney/unity-web-place/ubuntu/dists/quantal/main/binary-i386/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/gwibber-team/ppa/ubuntu/dists/quantal/main/source/Sources  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/gwibber-team/ppa/ubuntu/dists/quantal/main/binary-amd64/Packages  404  Not Found
, W:Failed to fetch http://ppa.launchpad.net/gwibber-team/ppa/ubuntu/dists/quantal/main/binary-i386/Packages  404  Not Found
, E:Some index files failed to download. They have been ignored, or old ones used instead.