Using Ajax and FireFox

Hi all,
I have created a new application 1month ago. In that application i
have a link Add New. This link is given using Ajax(<%= link_to_remote(
‘Add New’,
:update => “abc”,
:url =>{ :controller=>“xyz”,:action =>
:position => “after” ) %>)

and also i gave <%= javascript_include_tag ‘prototype’ %> to define
It worked good and i’m using that application since 1 month.

But today when i click on add new i’m not getting the form. Its giving
an error “Ajax not defined”.Even its not working in my local
machine.(all these things,i’m doing using FireFox).

So i tried in IE. Its working properly. So what might be the problem?
Why its not working in Firefox??

Thanks and Regards,