As of the release of Ubuntu 7.04 (Feisty Fawn), Nvu, a fully graphical web design program, is no longer available in the Universe repositories, since the Nvu project has been discontinued. Nvu has been revived with a new name, though--it's now called KompoZer.
* 7.10 (Gutsy Gibbon) - KompoZer is in the "universe" repository, so if you're using that release get them through apt/Synaptic.
For all other supported releases, use TonyYarusso's PPA on Launchpad.
Automatic Download and Installation
If using gutsy, merely make sure you have the universe repository component enabled (it is by default).
If using feisty, make sure to enable backports ("unsupported updates").
For other releases, you will need to edit your sources.list file. This can be done with the command 'gksu gedit /etc/apt/sources.list'. Add the one (and only one) of the following lines that matches the release you are running:
Save the file and close Gedit. Update apt by either running 'sudo apt-get update', or in Synaptic clicking the Reload button.
In the Package Installer, search for kompozer, and click on Install Package.
For PPA packages, you may need to approve installation of an "untrusted package".
KompoZer is accessible via Applications/Internet menu.