Before you apply a style sheet to a Web page, you can preview the
page in the Preview pane of CSS Designer. The Preview pane (the left area
of the editor) shows you how the currently defined styles are likely to look
when viewed in an external Web browser.
If you maximize the Preview pane, the file selected in the Project
Explorer view is immediately reflected in the sample Web page in the Preview
pane. If you want to see style effects in several Web pages, this feature
is beneficial because you can change the sample page in the Preview pane by
simply selecting a new file in the Project Explorer view.