First JSP + Glassfish app

I'm very beginner, I tried to make JSP application HelloWorld, very simple like on the youtube video here http://www.youtube.com/watch?v=m_33ZHYCjf8&feature=related, without changing almost anything

But on my computer I can't even start this simple HelloWorld application getting the error "Not found: The requested URL /HelloWorld/ was not found on this server"

I use Windows 7, Netbeans 6.9.1 and Glassfish v.3.

In WEB-INF directory I have only sun-web.xml like this:

<sun-web-app error-url="">
  <context-root>/HelloWorld</context-root>
  <class-loader delegate="true"/>
  <jsp-config>开发者_Python百科;
    <property name="keepgenerated" value="true">
      <description>Keep a copy of the generated servlet class' java code.</description>
    </property>
  </jsp-config>
</sun-web-app>

Please, can you direct me, what with this problem could be connected and what I can check, all the answers will be appreciated.

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Given your sun-web.xml, the URL should be something like yourhost/SayHello and not yourhost/HelloWorld.