Using CSS in Freewebs is a little different from Piczo. You actually just have to paste in the CSS code one time and when you change this code you will change the whole site. Here's how it works:
Step 1: Copy a CSS code like this the one under, without the style-tags. Paste the code in a new page you call CSS (or something else, it is up to you).
Step 2: After pasting the code save the page. Then copy the URL adress of the CSS page and paste it in this code where it says PAGE URL HERE:
Step 3: The code over has to be on ALL your pages! When you want change your CSS code you only have to change the page you called CSS and all the pages will be changed aswell. This will save you alot of time when you update.