I am new to Ubuntu and keep butting up against errors, such as this:

Package libpng12-dev is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source However the following packages replace it: libpng12-0

E: Unable to locate package subversion E: Package 'git-core' has no installation candidate E: Package 'build-essential' has no installation candidate E: Package 'autoconf' has no installation candidate E: Package 'libtool' has no installation candidate E: Unable to locate package libxml2-dev E: Unable to locate package libgeos-dev E: Unable to locate package libpq-dev E: Unable to locate package libbz2-dev E: Package 'proj' has no installation candidate E: Unable to locate package munin-node E: Unable to locate package munin E: Unable to locate package libprotobuf-c0-dev E: Unable to locate package protobuf-c-compiler E: Unable to locate package libfreetype6-dev E: Package 'libpng12-dev' has no installation candidate E: Unable to locate package libtiff4-dev E: Unable to locate package libicu-dev E: Unable to locate package libboost-all-dev E: Unable to locate package libgdal-dev E: Unable to locate package libcairo-dev E: Unable to locate package libcairomm-1.0-dev E: Couldn't find any package by regex 'libcairomm-1.0-dev' E: Unable to locate package apache2 E: Unable to locate package apache2-dev E: Unable to locate package libagg-dev

when I want to do this: sudo apt-get install subversion git-core tar unzip wget bzip2 build-essential autoconf libtool libxml2-dev libgeos-dev libpq-dev libbz2-dev proj munin-node munin libprotobuf-c0-dev protobuf-c-compiler libfreetype6-dev libpng12-dev libtiff4-dev libicu-dev libboost-all-dev libgdal-dev libcairo-dev libcairomm-1.0-dev apache2 apache2-dev libagg-dev.

Any help or advice would be greatly appreciated. Or referrals to other questions...