ok, so back to css and ssi now shall we?
CSS (Cascading Style Sheets) is nice but it is more for controling things like fonts, colors, certain spacings, and things of that nature.
SSI (Server Side Include's) are great as well, and can control anything that you can do with normal html.
so, liquid, think about what you need. If you're going to changing the format of the site a month down the line, than ssi will be probably be the way to go. If you just want to change the color scheme of the site from red to blue and back again a week later, CSS should do the trick. and now the doozy, really, you might want to look into CSS regardless because it is very nice to work with, and you can do some nifty things with it. So even if you end up using SSI, you should probably still check out CSS.
now decide what you think you need, and get back to us on it and we'll help you
-Brian