A very helpful thing is an external css-file because if you have one you do not need to edit every page if you change the site´s style. (for example when you put up a new layout or change the text-color) Here I will not show you how you can make an external css-file (therefor you have to read the other css-tutorials) I will show you how to include it into your page.
You just have to put in this code:
You have to put this code in every page in which the css-file has to affect the style.
If you have questions: mail me