Skip Windows Authentication with Selenium / Jenkins

I use Selenium IDE to create my tests I integrate these tests with selenium modules in Jenkins and all is OK.

My problem is that on my test site there is an authentication "windows" impossible to manage directly with selenium commands.

I try to change my base URL http://ift.tt/181Gk6H But it does not work (I use Firefox)

What would be the solutions to this problem? A JS solution perhaps? In my user-extensions.js ?

Thank you for help !