Kompozer was removed from the repository as it is no longer being maintained by its maintainer in the upstream(
As for your second question,
a suitable alternative for it would be Bluegriffon.
This is what it looks like:
To install it do the following steps:
Allow executing file as programcheckbox. (For security
About Bluegriffon, from its website:
BlueGriffon is a new WYSIWYG content editor for the World Wide Web.
Powered by Gecko, the rendering engine of Firefox, it's a modern and
robust solution to edit Web pages in conformance to the latest Web
Partially reference: https://askubuntu.com/a/136849/11932
The latest bluegriffon can also be installed from the getdeb repository, by doing the following steps:
wget -q -O - http://archive.getdeb.net/getdeb-archive.key | sudo apt-key add -
sudo sh -c 'echo "deb http://archive.getdeb.net/ubuntu precise-getdeb apps" >> /etc/apt/sources.list.d/getdeb.list'
sudo apt-get update && sudo apt-get install bluegriffon