Yes the "/" will make a big difference. whenever you reference anything with "/" , the requested resource will be searched for at the root of the server. However, if you do not specify "/" , then the resources will be searched in the current directory from which it is being referenced from.
The same following logic applies to both the struts action tag and the forward tag of the jsp as well.
This JSP will be searched for at the root of the server ( NOT the root of the project ). The URL will be localhost:8080/abc.jsp
However, just omit the "/" and the whole URL changes to localhost:8080/<project_context_name>/<some_dir>/abc.jsp
So yes , the "/" will make quite a huge of a difference.
Regards, Muhammad Saif Asif Mirza