1. Go to Page View.
2. Select File/New/Page or Web to open the Task Pane and choose Page Templates.
3. When the Page Templates dialog opens click on the Style Sheets tab. Choose Normal Style Sheet and click OK. FP will create a new empty style sheet and give the file the temporary name: new_page_1.css
4. You should also be presented with the 'Style' toolbar, although you may have to select it in view/toolbars if it doesn't show up.
Once you've created your style sheet you can apply it to your pages. Open the page you wish to link in Page View and go to Format/Style Sheet Links.
You can link the current page to a style sheet, or all your pages. Click on 'Add', locate your style sheet, and click OK. You'll then see your style sheet file appear in the list of linked style sheets. Keep repeating this process for each page that you wish to link. When you've finished click OK.
There isn't room here for a complete tutorial on CSS in FrontPage, but for a whole raft of information
click here click on the 'Web development' link and then on 'Cascading style sheets'.