求助!

帮我看一下,下面这段话是什么意思?

java.lang.NoClassDefFoundError: test/bbsreg
at test.bbsboard.<init>(bbsboard.java:42)
at _bbs._about__jsp._jspService(_about__jsp.java, Compiled Code)
at com.caucho.jsp.JavaPage.service(JavaPage.java:74)
at com.caucho.jsp.Page.subservice(Page.java:485)
at com.caucho.server.http.FilterChainPage.doFilter(FilterChainPage.java:181)
at com.caucho.server.http.Invocation.service(Invocation.java, Compiled Code)
at com.caucho.server.http.CacheInvocation.service(CacheInvocation.java, Compiled Code)
at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java, Compiled Code)
at com.caucho.server.http.HttpRequest.handleConnection(HttpRequest.java, Compiled Code)
at com.caucho.server.TcpConnection.run(TcpConnection.java, Compiled Code)
at java.lang.Thread.run(Thread.java:479)

谢谢!