Previewing a project before and during the editing of a project helps you notice the changes that are required. This way, you can be sure of the final output before you publish it.
You can change the number from 5 to your desired number of slides using the Preferences dialog box.
In Cp 7, the SWF and HTML5 previews are displayed using the Mongoose webserver integrated with Adobe Captivate. In cases where preview on the webserver is not supported (for example, if project includes Open URL or File, or Open Another Project actions), the preview appears in the default web browser.