The order of the CSS files matter . . .
The order of the CSS files tell the browser that your styles in main.css are more important than the styles in bootstrap.css, so the final page that loads is the customized web page.
<link rel="stylesheet" href="http://s3.amazonaws.com/codecademy-content/courses/ltp/css/bootstrap.css"> <link rel="stylesheet" href="main.css">
Overall, this says that the final style in css tab is the one that loads. If so, then why go through the trouble of putting all of the links before this in?