hi ,

just check the relative path in 
response.sendRedirect("some_path");
for e.g in iplanet web server, suppose all the jsp and html files are 
stored in
"some_drive:/A_folder/B_folder/jsp" folder, then the entire path 
from "some_drive:/A_folder/B_folder/jsp" can be mapped to "/jsp". That is, 
if "a.html" file is stored under, "some_drive:/A_folder/B_folder/jsp" 
folder, then you can access a.html in your jsp like this :

response.sendRedirect("/jsp/a.html");

please check your web server for such mappings. If you are not sure, then 
you need to give the entire absolute path. Hope it helps you...