When you view some kinds of files in Eclipse e.g. wsdl files the "wizard" shows you two tabs at the bottom right viz. "Design" and "Source".
This doesn't automatically happen with html or jsp files.
Right-click on the html or jsp file in the "Package Explorer" window and either "Open with - "
"Web Browser" (which just shows you the preview - note the the "Refresh" button at the top) or
"Web Page Editor" (which enables "Design / Preview" tabs). It also splits the screen in half so you can see both at the same time.
Ensure that "Windows / Preferences / General / Web Browser" option is set to "Use internal web browser".