Javascript - Window open, use CDN

Javascript - Window open, use CDN

Simple question. I cannot get a new opened window to use CSS.
var previewWindow = window.open();
$(previewWindow.document.body).append(data);
The data is just a stringbuilder generating html from our backend.
The problem is, I want the newly opened tab/window to use Twitter
bootstrap, either CDN or use the file.
I cannot get it to work with, what I tought should be the solution
$(previewWindow.document.head).append('cdn or path goes here')
I cannot seem to find anyone else with this problem, or I need a lecture
in Google.