Thread: HTTP Status 404

hello..
i am a beginne in java servlet. i would like to run my first application in it for my project.
i get an error in trying to run my first HelloServlet class. the error is

HTTP Status 404 - /aas/HelloServlet

--------------------------------------------------------------------------------

type Status report

message /aas/HelloServlet

description The requested resource (/aas/HelloServlet) is not available.


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Apache Tomcat/5.5.27

where is aas is a folder under webappl folder to hold my system.
i set the class path=C:\Program Files\Java\jdk1.5.0_16\bin;C:\apache-tomcat-5.5.27\bin;c:\apache-tomcat-5.5.27\common\lib\servlet-api.jar;C:\apache-tomcat-5.5.27\webapps\aas\WEB-INF\classes;C:\apache-tomcat-5.5.27\common\lib\jsp-api.jar

i set the java home=C:\Program Files\Java\jdk1.5.0_16


and the web.xml contains:

  <?xml version="1.0" encoding="ISO-8859-1" ?> 
- <!-- 
  --> 
- <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4">
  <display-name>Welcome to Tomcat</display-name> 
  <description>Welcome to Tomcat</description> 
- <!--  JSPC servlet mappings start 
  --> 
- <servlet>
  <servlet-name>HelloServlet</servlet-name> 
  <servlet-class>HelloServlet</servlet-class> 
  </servlet>
- <servlet-mapping>
  <servlet-name>HelloServlet</servlet-name> 
  <url-pattern>/HelloServlet</url-pattern> 
  </servlet-mapping>
- <!--  JSPC servlet mappings end 
  --> 
  </web-app>

i really want to do that to move to the programming..
thank you a lot..