You probably put it in the wrong place.
Are you sure you logged into the correct user? You can check this by going to manage domains in the panel and looking in the column labeled "web hosting"
(replace all caps with your info)
when you log into the ftp sever, you will be placed in the directory /home/USER/
in that directory you should see a directory created by the system called DOMAINNAME.COM, change to that directory.
upload your nav.html here
Now in your browser navigate to DOMAINNAME.COM/nav.html
the previous poster ronthai is correct, this is a discussion forum for users to help other users, you must give all the information to receive help. If by "Kindly resolve the this issues" you meant that you expected to post here and have dreamhost magically "fix" it for you then you are wrong, you must open a ticket with customer support for that.