Today when I was doing something my colleague asked me about what version of JSP and Servlet are you using. Untill now I never bothered about this, but later found a way for this. below are the lines of code to know what version of servlet you are running, version of JSP and application server you are running.
Servlet Version :
<%= session.getServletContext().getMajorVersion() %>.
<%= session.getServletContext().getMinorVersion() %>
JSP Version :
Server Version : <%= application.getServerInfo()%>