I have written this code for servlet
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class Httpservlet1 extends HttpServlet
{
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException
{
String color = request.getParameter("color");
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
pw.println("<B>The selected color is: ");
pw.println(color);
pw.close();
}
}
i have compiled it and its corresponding html file action attribute value is
action="http://localhost:8765/HS/HTTPSERVLET">
and
web.xml contains
servlet-name four
servlet-class Httpservlet1
servlet-name four
url-pattern /HTTPSERVLET in xml code format still its showing error message on running it

Perhaps your web.xml is not properly formed.
It works OK for me.