You may want to try Kompozer instead.
Thanks. I tried Kompozer on an existing XHTML 1.0 Transitional page that passes W3C markup validation fine, but Kompozer clearly shows where it comes from:
It has the same annoying habit as Composer in SeaMonkey of changing source formatting (hard-wrapping text), even when "Retain original source formatting" is selected in preferences.
It also adds by itself returns (<br /> tags) when I do nothing but adding some text to an existing paragraph without ever touching the enter or return key.
And it changed by itself coding in a list (with CSS showing as a menu) from
thus completely destroying the appearance of the whole page.
It would be nice to have a simple WYSIWYG editor that respects existing code.