By default, Dreamweaver uses Cascading Style Sheets (CSS) to format text. The styles that you apply to text using the Property inspector or menu commands create CSS rules that are embedded in the head of the current document. CSS styles provide you with greater flexibility and control over the appearance of your page, from the precise positioning of layout to specific fonts and text styles.
You can also use the CSS Styles panel to create and edit CSS rules and properties. The CSS Styles panel is a much more robust editor than the Property inspector, and displays all CSS rules defined for the current document, whether those rules are embedded in the head of the document or in an external style sheet. Macromedia recommends that you use the CSS Styles panel (rather than the Property inspector) as the primary tool for creating and editing your CSS. As a result, your code will be cleaner and easier to maintain.
In addition to styles and style sheets you create, you can use style sheets that come with Dreamweaver to apply styles to your documents. (See Creating a document based on a Dreamweaver design file.)