what do you mean by mapping A -> B B -> C ?
do you mean forward?

there are several ways to achieve that.
one will be to use jsf and action mapping. in faces-config.xml you specify the mapping after action.

another way, more simple is to use <%= request.getContextPath()%> to build the base path relative to the portal page.
for example:

/inside portlet jsp/

i couldn't paste the code for some reason

To post code: select the code and click the Code button, that will surround the code with [ code ] [ /code ] brackets.

<link rel="stylesheet" type="text/css" href="<%= request.getContextPath()%>/css/displaytag.css">