Peacock is a GUI-based HTML Editor for GTK+/GNOME.
Its still in its infancy. Very, very alpha.
The version number speaks for itself.  Its not a WYSIWYG HTML Editor.
Its like Homesite for Win32 (or much closer to home), Bluefish for GTK+.
You have to type your HTML yourself. But there are these 'HTML Toolbars'
which allow easy and quick entry of commonly used tags, thus saving you
time and keystrokes. 

http://peacock.sourceforge.net/