Ashton0603,
[html]
<center></center>
[/html]
is deprecated, this is a posh way of saying that you shouldn't use it anymore. Not because some bolt of lightning will strike you but because it will cause you confusion when coding.
The stylesheet should do all (99%) of the layout for you. If you separate layout from content then you will keep things simpler overall, especially when your site is dynamically generated, like ZenCart.
the logic of the stylesheet will become appreant very quickly as long as you don't overthink it.
#nw {
text-align:center;
vertical-align:top;
margin:0 auto;
}
means: make all text in the div id nw centred, align with the top of the parent div box and with a zero top and bottom margin, but style everything (not just text) with an equal left and right margin.
so, if you were to take the <body> element and style it in the css thus:
body {text-align: center}
then all text within the body will be centred.
Remember though that stylesheets have a hierarchy too, so if you take in individual element or division(div) and style it separately after another rule then that statement will be followed, so:
body {text-align: center}
p {text-align: left}
would mean, all text is centred, but <p> text is align to the left.
to understand the flow though:
p {text-align: center}
p {text-align: left}
in the same stylesheet, in this order would mean that all <p> text is aligned left, because that rule came last and is therefore adhered to.
Correct use of the stylesheet will mean that <center></center> as with other inline styles will become obsolete to you (for the most part). Rightly so, imagine having to go through 12Mb of code looking for all of the tags inline with the html/php!
Hope that this helps!
Dave