hi Paul,
The first thing you have to know is that jsp IS Servlet.
The first time a jsp page is used, it is "compiled" by the jsp engine to obtain.... a servlet.
Now let's try to answer your question.
If you are a programmer only interested in Client presentation, HTML,XML, the learn only the JSP. It is quite simple to undersatnd with a html background.
But if you need to become a
J2EE programmer, using MVC architecture, mainly interested in Server-side development then you have to fully understand what a JSP is.
Thus, learn the Servlet API first. Jsp is just a simplified stuff of the Servlet API.
Hope this is note to confused... :-(