Resolved this issue by making changes in the rails.validations.js
First i have generated the js via
rails g client_side_validations:copy_assets
On line 550
changed
return "//" + window.location.host + "//" + ClientSideValidations.remote_validators_prefix + "/validators/" + validator;
to
return "//" + window.location.host + ClientSideValidations.remote_validators_prefix + "/validators/" + validator;
Did this because the ajax request was something like this
http://localhost:3000//validators/uniqueness?case_sensitive=false&user%5Blogin%5D=john&_=1365516039852
You can notice there is two slashes
http://localhost:3000//