When I cannot find a package in the repositories that I want to install I go
to the Debian package search and look for that software as a debian package.
Here is KompoZer's: https://packages.debian.org/squeeze/kompozer
Once there I select a download that corresponds to my architecture. e.g.
amd64 for me.
Once downloaded I open a terminal window and cd to the directory that I
downloaded the .deb file to.
once there I run the command dpkg -i file.deb
That should get you where you need to be, unless there are dependencies you
don't have.
Of course any dependencies you will have to track down either in the
repositories or by getting the debian package for that particular dependency.
I hope this helps.
GrimLok
