i use go live 5.0 to design my sites. i do not use the layout mode.
source and preview mode are staples along with a healthy dose of firefox
to make sure my progress is to standards.
i write css in the document and export when finished with the page.
after export if i need to tweak (usually have to) i open the css file
and right click and chose "edit source code" and do what i need to do
there. go live is my html editor and w3c is my validator for that html
and for the css.
i generally ignore go live warnings except when i have a link out of
place or incomplete.
List wiki/FAQ -- http://css-discuss.incutio.com/
Supported by evolt.org -- http://www.evolt.org/help_support_evolt/