how to show custom Application stopped and Service unavailable error pages in netweaver 7.3

HI ,

i am trying to show the custom error pages for Application stoped and service unavilable in 7.3 portal.

i find out the way to change the paramters for application stopped as per the below URL:

http://help.sap.com/saphelp_nw73/helpdata/en/4a/8f8f1aeb323896e10000000a42189c/content.htm

and was able to successfully change the parameter but i cant see the changed page .. when application is stopped. do i need to make anything else.

also for service unavailable i am not able to find out the parameter settings. can some one help me on this.