What are "Failed to fetch cdrom" errors in Update Manager and how do I fix them?

Question

Possible Duplicate:
Failed to download repository information due to missing CDROM

Whenever I run update-manager, I am getting the following error:

Failed to fetch cdrom://Ubuntu 10.04.2 LTS _Lucid Lynx_ - Release amd64 (20110211.1)/dists/lucid/main/binary-amd64/Packages.gz  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
Failed to fetch cdrom://Ubuntu 10.04.2 LTS _Lucid Lynx_ - Release amd64 (20110211.1)/dists/lucid/restricted/binary-amd64/Packages.gz  Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
Failed to fetch http://ppa.launchpad.net/qwibber-daily/ppa/ubuntu/dists/lucid/main/binary-amd64/Packages.gz  404  Not Found

• How can I get rid of these errors?
• What is this error trying to tell me?