A style sheet can be associated with any number of HTML topics or a new topic. If you create a style sheet in a project and apply it to a new topic, all topics you create later use the new style sheet. You can link a topic to another style sheet, if necessary.
Link a Style Sheet to Topics or Master Pages
To link a style sheet, select one or more topics from the topic list, right-click, select Properties, and click on the Appearance tab.
Select a style sheet in the list or navigate to a new style sheet on your computer. You can click New to create a style sheet or edit the style sheet in the Styles Dialog Box.
Create a Style Sheet
The default.css is the default style sheet until you create a style sheet or link another style sheet to a new topic. To create a style sheet, go to the Edit tab and in the CSS section, click on the New Stylesheet.
In the Name field, type a filename including the .css extension and select a folder location. If you would like to base your new style sheet on an existing one, select an existing style in the Copy Styles From dropdown menu. Click Create to open the Styles dialog box to create a new style and then click on OK.