Did u set the classpath for the jdk and the path where you placed the servlet.

%WL_HOME%myserver\servletclasses.

Try this option and also try to edit the weblogic.properties file.

Find for

#weblogic.httpd.register.servlets=weblogic.servlet.ServletServlet

and replace it by

weblogic.httpd.register.servlets=weblogic.servlet.ServletServlet