(Adapted from https://help.ubuntu.com/community/InstallKompozer)

All the commands listed on this page must be entered by copying and pasting into a terminal window.

First, install the dependencies:

sudo apt-get install libatk1.0-0 libc6 libcairo2 libfontconfig1 libfreetype6 libgdk-pixbuf2.0-0 libglib2.0-0 libgtk2.0-0 libidl0 libnspr4 libnss3 libpango1.0-0 libpng12-0 libstdc++6 libx11-6 libxft2 libxinerama1 libxrender1 libxt6 zlib1g

Then, get the two packages, and install them in the correct order. (Copy and paste each line individually.)

For 32 bit systems:

wget https://launchpad.net/ubuntu/+archive/primary/+files/kompozer-data_0.8%7Eb3.dfsg.1-0.1ubuntu2_all.deb
wget https://launchpad.net/ubuntu/+archive/primary/+files/kompozer_0.8%7Eb3.dfsg.1-0.1ubuntu2_i386.deb
sudo dpkg -i kompozer-data_0.8~b3.dfsg.1-0.1ubuntu2_all.deb
sudo dpkg -i kompozer_0.8~b3.dfsg.1-0.1ubuntu2_i386.deb

For 64 bit systems:

wget https://launchpad.net/ubuntu/+archive/primary/+files/kompozer-data_0.8%7Eb3.dfsg.1-0.1ubuntu2_all.deb
wget https://launchpad.net/ubuntu/+archive/primary/+files/kompozer_0.8%7Eb3.dfsg.1-0.1ubuntu2_amd64.deb
sudo dpkg -i kompozer-data_0.8~b3.dfsg.1-0.1ubuntu2_all.deb
sudo dpkg -i kompozer_0.8~b3.dfsg.1-0.1ubuntu2_amd64.deb

You will now find KompoZer in the menu.