BLANK PAGE on Joomla! 2.5

Hi,
i 've just install the plugin on a joomla site 2.5.28 and the site stop working with blank page also on admin, through ftp i managed to get the site back normal again, the problem is when i enable System - Web357 Cookies Policy Notification Bar i get on admin 500 - JHTML: bootstrap not supported, maybe this help you to identify the problem.

I can't help, but you have to know, Joomla 2.5 is at
the end of life.

I think "bootstrap not supported" is correct. As far as I remember it came with Joomla 3.

And: Move to Joomla 3 asap – it is just a question of time until you get hacked.