Quanta is web development environment for KDE but you still can install for gnome. Your page can be saved as HTML, PHP and XML format. It also supports CSS.
From Ubuntu Terminal screen (Applications > Accessories > Terminal), type:
taufanlubis@toshiba:~$ sudo apt-get install quanta
[sudo] password for taufanlubis:
Reading package lists… Done
Building dependency tree
Reading state information… Done