Ubuntu Servers :: Tomcat Manager Doesn't Work?

I'm really new with Ubuntu and have the following problem:I installed successfully sun-java6-jdk using apt-get install sun-java6-jdk Then set up the JAVA_HOME environment variable to "/usr/lib/jvm/java-6-sun-1.6.0.20"

And then installed successfully tomcat6 using apt-get install tomcat6 apt-get install tomcat6-admin tomcat6-examples tomcat6-docs Everything seem to be right, when I try the browser with http://localhost:8080 return a webpage with "It works !" and other text

But, if I try http://localhost:8080/manager/html then returns 404 error, the error is something like "The required resource (manager/html) is not available" (that is my translation from the spanish text "El recurso requerido (/manager/html) no est disponible")

[Code]..