What does the normalise.css mean?

Hello, James! Stuart explained you about normalize.css already, bus as if you have additional question, I'll explain a little bit more about it. You are not obliged to use that file (normalize.css) or to use particularly this one. I mean that your page won't "crash" without it. But you should do it as a very good, useful practice if you really care about how your webpage will look out in defferent browsers . For example, developing your page you assigned your header or other element margins to look good. You finished it and it looks nice in your browser. But it is possible that users of your page will have other browser with another default styles, so for that person your page will look differently and possibly more worse than you did it as you couldn't consider all possible features and new versions. To prevent maximally such unpleasant situations you use normalize.css and so your page will be still nice as you wanted, developing it. And I said you are not obliged to use this one as there are several ways to do it. As to me I include sometimes Eric Meyer’s “Reset CSS”, which is used for same purposes.

So it is enough to download that file and reference it to HTML! Include a link to normalize.css or the same one before your own styles (main.css) as they can overwite them if you change that order.