MY_Controller extension problem

[eluser]jacobson[/eluser]
Hello, I have a problem with facebook. I want the "log in with facebook" button to be visible on all pages. This means that I need the whole code in controller/action related with facebook (about 20 lines).I wanted to put all of this into just one file. I wanted to use core extension My_Controller. I added all of this lines to __construct to My_Controller and added to my site_controlle to extend My_Controller but it's not working. Facebook is not visible :/ Am I doing something wrong ? is there any other possible solution for this problem ?