Closing a single Web page or a whole Web site full of open pages is easy:
To close the page that's open and displayed in the editing window, choose File Close or click the X in the upper-right corner of the editing window. (If you haven't saved yet, don't worry. Expression Web prompts you to save your changes before it closes the page.)
If you want to close an open page that isn't the active page, click its tab and then close it. You can also right-click a page's tab then choose Close from the pop-up menu.
To close all pages in a Web site (which closes the entire Web site), choose File Close Site; or click the X in the upper-right corner of the Expression Web workspace.