Nested list navigation not displaying in themes

Introduction

I’ve recently been learning the ropes with CMS, and updating my HTML knowledge from 4.0, to XHTML and CSS. It’s still fairly new to me, but I understand the concepts, but haven’t had much practical experience yet.

It seems to me that learning about CMS/Blogs, and XHTML (strict) / CSS, at the same time is a bit Jekyll & Hyde.

Where CMS makes it easy by doing all the work for you, studying standards compliant XHTML and CSS puts all the complexity back in again. I’m trying to do both, and I’m getting a bit overloaded with information!

Anyway, to my problem.

Having installed WP on my web space, everything works fine and it seems pretty intuitive.

I got quite excited about creating a nice usable, good looking, compliant site, and set up a very basic structure. I then had a look for some themes to base the site on (and maybe customise the images at some point).

What I wanted first of all was basic working navigation. I have a few nested sub navigation headings eg…

.Nav 1
.Nav 2
.Nav 3
..Nav 3a
..Nav 3b
.Nav4

…Which works fine with the standard WP themes.

However when I chose the new themes I’ve downloaded from the Theme Directory (where I’ve chosen horizontal navigation), I find that the nested navigation (3a, 3b) doesn’t appear.

In addition, if more navigation items are added, than can be occupied in the width of the nav area, they too disappear.

My understanding of standards compliant XHTML/CSS was that there are supposed to be no ‘size restrictions’ (hence preferring to use em and % units, rather than px, pt etc), so is there a simple reason why these WP templates don’t accommodate more complex navigation?

I wouldn’t know where to start if it requires modification of the CSS file…

Thanks for reading and I appreciate any help offered.