Please UseCodeTags when posting code or configuration. Unformatted code and configuration is unnecessarily difficult to read. You can edit your post by using the button.
Also note that the directory structure is impossible to understand without formatting. Also, please TellTheDetails: without knowing under what circumstances the error happens, it's much more difficult to help. Also, if there is a stack trace, please include it.
I don't see your web.xml file, so we have no way of known if the servlet is configured correctly. Is there a stack trace? Where are the servlet classes being deployed to? There's no indication of where your class files located in your directory hierarchy.