One of the great things about SharePoint Designer 2007 is the much improved CSS support. When customizing SharePoint sites, there is now a much cleaner interfacce for dealing with multiple stylesheets.One common scenario might be that you want to customize a variations based WCM (publishing) site. Below lists a couple of quick steps to get you started as well as a couple of visuals for reference.
1) Open your Internet Presense, or Publishing Site if using variations using File, Open Site in SharePoint Designer 2007
2) From the left menu locate and open the _catalogs directory, inside you will find the master pages library where the files you want to edit are stored.
3) Open the TopNavFlyouts.master (I’m as confused as anyone on the name so don’t ask)
4) With the TopNavFlyouts.master open, you should notice a new set of menu’s in the right toolbar – towards the bottom you will see the “manage styles” area. This area is of particular interest as it lists all the style-sheets applied to a particular page and to the best of my knowledge in the order they are referenced which means each layer “down” can over-ride the previous. Double clicking any of these style-sheets will open it for editing at which time you will notice a second level of items in the manage styles menu (the classes). Double clicking any of these bring you directly to the code for editing.
One great tip: While on your TopNavFlyouts.master page select the options drop down in your manage styles pane – there is an option that lets you show ONLY styles which are applicable to the page you are editing. (screenshot below).
You can use the visuals below as a reference: