Why the following code does not display Hello world! in Split view on the "design" side? When I upload the file onto the server and try to view it in the browser everything displays normally.
This is normal, design view is simply a way of either creating your website using the wysiwyg method or if you code the website it is a way of getting an idea what the site will look like static. Design view doesn't run any scripts, which is why in the more recent versions of dreamweaver we have LiveView which does run the scripts and allow you to interact with drop down menus and the like, which you can't do in DesignView.
Thank you very much!