Yes you can edit those just as if they were .
html pages or .htm pages. The only reason they are saved as .
php pages is because there is
php coding somewhere within the sites that requires the
php file type.
Dreamweaver opens a
php page as I'm sure many other editors must do. Once you are in the
php page, you can edit the
html and then look for the
css to edit that as well. The
css is probably saved in a file that ends in .
css or it could be right in the head area of the
php page.