Hi,
JDK(Java Development Kit) is meant for developing Java Applications and Applets. It does not include the Servlet or JSP implementations with it. These specifications are implemented separately and are ported with Web Servers like JavaWebServer, Tomcat, JRun, iPlanet, WebLogic, etc and also with J2EE SDK. So once you have any of the Web server, you have the Servlet/JSP implementation in hand(technically in your CLASSPATH) and hence you can develop Servlet/JSP applications and can deploy them in your server. JSDK(Java Servlet Development Kit) and JSWDK(Java Server Web Development Kit) are released to support the development of Servlet/JSP and then later deploying it in the WebServer. They are not meant for production quality Web deployment. As most of the WebServers includes the Servlet/JSP implementations the Sun people have stopped the new updates for JSDK and JSWDK. So you don't need to use JSDK/JSWDK for development if you have a WebServer that supports Servlet/JSP.