Saving your web site
In WYSIWYG Web Builder you never edit your HTML pages directly. Instead a project file is being used (.wbs) which stores all pages of your website within a single file. Everytime you want to edit your website you open this project file.
To save your web site (including all pages it contains), select File->Save Web Site for the menu and enter a name for the project.
Web Builder uses the extension .wbs (Web Builder Site) to save the project files, to save your page as HTML you'll need to Publish your pages.
Related topic:
Publishing your web pages