Class not found in IBMWebSphere [Closed]

I deployed the webapplication in explored format. The JSP page works fine, but I always got
“Error 404: File not found: servlet/ClientCertTest” error message.

And in the log, it shows class ClientCertTest not found. But I could found my class under WEB-INF/classes/abc directory.

Here is my web.xml.
<?xml version=”1.0″ encoding=”UTF-8″?>
<!DOCTYPE web-app PUBLIC “-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN” “http://java.sun.com/dtd/web-app_2_3.dtd”&gt;
<web-app>
<servlet>
<servlet-name>ClientCertTest</servlet-name>
<display-name>Client Cert test on IBMWebSphere</display-name>
<description>Client Cert test on IBMWebSphere</description>
<servlet-class>abc.ClientCertTest</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>ClientCertTest</servlet-name>
<url-pattern>/servlet/ClientCertTest</url-pattern>
</servlet-mapping>
</web-app>