how to redisplay the jsp with entered info

I've a servlet that checks the info user entered in a jsp, if it found an error 
it dispatch the same JSP.  Everything seems be working ok except these two 
problems:
1) How can I redisplay the jsp with the data that user has entered?
2) User is able to use the browser back button to get to the previous jsp page. 
 Is there a way to stop that?
 
Here is the code in servlet the I use to redisplay the jsp:  (errors is a 
Vector object)
if (errors != null && errors.size() > 0) {
    String url = "/MyCrtAcctStep1.jsp";
    ServletContext sc = getServletContext();
    RequestDispatcher rd = sc.getRequestDispatcher(url);
    rd.forward(req, res);
}
 
thanks