The theme in question:

http://www.plaintxt.org/themes/sandbox/

Interesting that it's left-aligned?

Well, to be clear Sandbox isn't just left-aligned that's the default style that comes prepackaged with the system.

Sandbox is, for lack of a better word, the perfect theme for web designers who use CSS to style websites and don't enjoy mucking through lines of html and php code. The basic principal of Sandbox is that all the possible CSS class and ID hooks are already built in into the template. It is possible, without touching the XHTML, to make the theme into just about anything you want. left aligned sidebar, right aligned sidebar, left and right aligned sidebars, Bottom aligned sidebars. Basically the style is super loaded with what they coin "Dynamic, semantic class selectors"

In principal it means that every little bit of HTML is already loaded with a specific and standardized class or ID elements. For the layman it means that if you want the title of your blog page to be red, you can make it red.

h1#blog-title { color: red; }

What makes sandbox so different from other systems is, if you want to make the title of all the pages in the category of "fish" blue, the template is already loaded with the selectors to do so.

body.s-category-fish h1#blog-title { color: blue; }

Or if you want to make pages by by user "Johnathan" neon green - presto. All the hooks are built in to change any element on a per page or site wide basis.

body.page-author-jonathan { background-color: green; }

The upside to all this technical mumbo-jumbo is that once you learn the straight forward nomenclature of sandbox, you really don't need to touch the WordPress code other than to move block elements around or change the content. This means that although all your site's may be styled differently, they all share the same XHML code base. That speeds up development and gives you the opportunity to make a living if you do this stuff for money.

There are of course many more "Dynamic, semantic class selectors", but I thought it better to start off slow. :)

Sorry if that was again too technical.

True, but in terms of bandwidth, XHTML is only a very small part of the equation. Using Sandbox removes the need for some presentational javascript rendering pages far faster.

K2 for instance has been ported to Sandbox and the sandbox version loads in half the time in Firefox because of the lack of need of some javascript libraries. The full K2 has also incorporated the sandbox "Dynamic, semantic class selectors" because of their usefulness in style control.

Also, the semantic classes really don't add much to the code and because the code is semantic, the class and ID selectors are not superfluous. Every piece of code, aside from one bizarre exception (ul.xoxo), is semantically based and not added in an ad hoc fashion. So while the code may be bloated for some users, it's also completely standardized and removable if you so wish. It is a theme after all, so it's purpose is to be as flexible as possible to the largest number of users. Designers and developers, with knowledge of WordPress templates, can strip out unused classes in their templates if they see fit slimming down code bloat.