Adding new pages
The 'Define New' button > Link opens in a new window?
You can find this field by clicking the 'Define New' button for a new page, or the 'Define' button for an existing page.
This just means that when a viewer clicks on this link, it will open in a new window or tab in the viewer's browser. You should also toggle this to YES if this page you've defined is a Menu Link that points the site viewer to another website. Otherwise the viewer will leave your site, and it will be replaced by the new website in the viewer's browser window.