An exception occurred processing JSP page

estou tentando rodar essa aplicação simples de um exemplo que estou estudando passo a passo na apostila algaworks e está dando esse erro.
alguem sabe oq seja ? (ja procurei no forum e no google mas os erros do pessoal são outros e não esse).

[code]org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 13

10: Minha primeira aplicação
11:
12:
13: <f:view>
14: <h:form>
15: <h:outputText value="#{inscricaoBean.mensagem}"
16: rendered="#{not empty inscricaoBean.mensagem}"/>[/code]

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:505)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
root cause

java.lang.RuntimeException: Cannot find FacesContext
javax.faces.webapp.UIComponentClassicTagBase.getFacesContext(UIComponentClassicTagBase.java:1811)
javax.faces.webapp.UIComponentClassicTagBase.setJspId(UIComponentClassicTagBase.java:1628)
org.apache.jsp.index_jsp._jspx_meth_f_005fview_005f0(index_jsp.java:110)
org.apache.jsp.index_jsp._jspService(index_jsp.java:84)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.