How not to break a css url link on ruby on rails?

[Trammibre]

I am developing an application with ruby on rails, and i'm using bootstrap to upgrade my css.My question is:if i have the next url link: link href="http://stackoverflow.com/questions/15545280/css/bootstrap.css" rel="stylesheet"how can i redefine the url to be a relative one, thus it will not break if i rearrange myproject's files?thank you.