Ubuntu appears apt-get:package has no installation cand

There was a problem with the package have no installation candidate when installing the software today, such as:

# apt-get Install <packagename>
Reading Package Lists ... Done
Building Dependency Tree ... Done
Package aptitude are not available, but are referred to by the another package.
This may mean and the package are missing, has been obsoleted, or
is only available from another source
e:package <packagename> has no installation candidate

Here's how to fix it:
# Apt-get Update
# Apt-get Upgrade
# Apt-get Install <packagename>

This will allow the apt-get to be used normally ~

Add a third-party address:

sudo add-apt-repository "Deb http://archive.canonical.com/lucid partner"

sudo apt-get update

Ubuntu appears apt-get:package has no installation cand