Active NRebuild is a rebuild of NRebuild. NRebuild claims to be different with clear and predictable CSS.
Download Active NRebuild from drupal.org/project/active_n_rebuild. This version is 6.x-1.54 from 2010-Aug-03, a 53.63 KB download.
Regions
Validation
This theme validates as CSS 3. 
Validation against the older CSS 2.1 produces the following errors.
URI : http://d-theme.com/sites/all/themes/active_n_rebuild/nx-style.css
79 tr.taxonomy-term-preview Property opacity doesn't exist in CSS level 2.1 but exists in [css3] : 0.5
83 tr.menu-disabled Property opacity doesn't exist in CSS level 2.1 but exists in [css3] : 0.5
Wave did not detect accessibility errors.
The layout is too narrow for the sites I build. There is nothing in the right hand column but the space is wasted. At a minimum I expect documentation that tells me how to use the right hand column space for the content when there are no blocks in the right hand column or to increase the overall width.
In the middle of the main CSS file, I found the following lines that appear to control the width. Almost everything else has a width of 100%. The combination does not explain why the overall width is limited.
.column_1 .min_size {width: 200px}
.column_2 .min_size {width: 300px}
.column_3 .min_size {width: 200px}
.column_1 {width: 200px; background: #f5f5f5}
.column_2 {}
.column_3 {width: 200px; background: #f5f5f5}
I asked the developer. The reply:
Overall width:
.page_struct-page-acceptor {width: 890px} - for 890px
.page_struct-page-acceptor {width: 900px} - for 900px
.page_struct-page-acceptor {width: auto} - for fluid layout
The page structure is a mixture of tables and divisions that is bad design practice. Tables are a way of laying out a page for very old browsers. Divisions are the modern way to layout non tabular data. Choose one. Do not mix.
I asked the developer about making some small changes for XHTML 1.0 Strict. The reply:
This theme with Transitional layout. It will never be Strict!
So this theme is for people supporting older browsers.
Example HTML
Here are example HTML elements to see how they are formatted by this theme.
<a href="?x">link 1</a>: link 1 This is a test of a link you have not visited. See how links are highlighted. Hover your mouse over this link to see any hover effects that might be used then select the link to see the link displayed as visited.
<a href="?y">link 2</a>: link 2 Leave this link unselected as a comparison link you have not visited.
<abbr title="abbreviation">abbr</abbr>: abbreviation
<acronym title="Cyclic Redundancy Checksum">CRC</acronym>: CRC
<blockquote>blockquote</blockquote>:
blockquote
<cite>cite</cite>: cite
<code>code</code>: code
<div>div</div>:
div
<form> and <input>: The the comments form at the end of this page (if you are logged in).
<em>em</em>: em
<h1>h1</h1> is usually the top heading in the page. Repeating h1 in this test would break heading nesting.
<h2>h2</h2>:
h2
<h3>h3</h3>:
h3
<h4>h4</h4>:
h4
<h5>h5</h5>:
h5
<h6>h6</h6>:
h6
<hr />:
<ol><li>li</li></ol>:
- li
<p>paragraph</p>:
paragraph
<pre>.h3
{
font-size: 1.17em;
}</pre>
.h3
{
font-size: 1.17em;
}
<q>quote</q>: quote
<span>span</span>: span
<strong>strong</strong>: strong
<table><thead><tr><td>th1</td><td>th2</td></tr></thead>
<tbody>
<tr><td>td1</td><td>td2</td></tr>
<tr><td>td3</td><td>td4</td></tr>
</tbody>
</table>:
<ul><li>li</li></ul>: