1. Mini-goals. If a large amount of content is divided up into small chunks, the mind is able to tackle each portion at a time, and make mini-accomplishments. On the contrary, a large, monolithic piece of text seems insurmountable. Essentially, by cutting the text up, we're setting small goals for our readers, a tool often used in psychology.
   
2. Ease on the eyes. When text is spread out across a large width, people get lost and re-read large portions of text, get frustrated, and eventually quit trying. In smaller widths, it's much easier to maintain focus, because the eye can maintain an overview of the entire line without moving left to right.
   
3. Familiarity. Almost every large text book, newspaper, and magazine that we have read since childhood has used this same formatting. People are creatures of habit. Give them something they're used to, and they'll eat it up faster than something "better" or "more creative".

Code How do I post code blocks?

<table width="100%" cellpadding="0" cellspacing="0" border="0">
    <tr>
        <td width="50%" valign="top">
            <p>Columns in text are a very handy tool.
            Unfortunately, most designers don't use
            them because they're tedious to 
            implement.</p>
        </td>
        <td><img src="./images/spacer.gif" width="20" height="1"></td>
        <td width="50%" valign="top">
            <p>However, if you take the time and effort
            of putting them into use, you'll find 
            that they really add to the aesthetics 
            and functionality of your work.</p>
        </td>
    </tr>
</table>