Hello Vijaya,
Well, we have not tested it with Joomla 2.5. But it is good to know that it is working for you at local-end.
There is a small fix, which you need to do it manually now or we'll release it later.
Edit the file : Root => plugins => system => f90_registration_validation => f90_registration_validation.php
as line number 34 replace
$doc->addScript('plugins/'.$this->_type.'/'.$this->_name.'/tmpl/validation.js');
with
$doc->addScript('/plugins/'.$this->_type.'/'.$this->_name.'/tmpl/validation.js');
This issue is occurring due to different server type, probably you are using nginx on your live site.