what about this one?

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Servlet execution threw an exception
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)

root cause

java.lang.ClassFormatError: com/mysql/jdbc/ConnectionImpl
com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:283)
java.sql.DriverManager.getConnection(DriverManager.java:582)
java.sql.DriverManager.getConnection(DriverManager.java:185)
JspDBSolution.KidsBooksPage.init(KidsBooksPage.java:20)
JspDBSolution.BookStoreServlet.processRequest(BookStoreServlet.java:34)
JspDBSolution.BookStoreServlet.doGet(BookStoreServlet.java:90)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)

what about this one?

What do you mean by that ??
If you have a valid problem then create a new thread, do not simply hijack old threads.
Also post your analysis of the problem what are your thoughts, what do think is the root cause and what did you try to correct the problem.
Simply posting the problem without giving us any background information about the web application nine times out of ten isn't going to help much.