title: Which direction is better for sorting multi-column lists?
body: <p>Please note, I'm not asking how to implement or code a multi-column list. </p>
  
  <p>There are two ways to sort multi-column lists: horizontal and vertical. Many of the Microsoft System.Web.UI.WebControls have a RepeatDirection property that offers these two options. I'm sure other frameworks also offer these direction options.  </p>
  
  <p>Below are samples of the two options:</p>
  
  <p>Horizontal sorting (alphabetical)</p>
  
  <pre><code>* Ash      * Beech      * Cedar
  * Date     * Elm        * Fir
  * Grape    * Hawthorn   * Ivy
  </code></pre>
  
  <p>Horizontal sorting (numeric)</p>
  
  <pre><code>1. Ash      2. Beech       3. Cedar
  4. Date     5. Elm         6. Fir
  7. Grape    8. Hawthorn    9. Ivy
  </code></pre>
  
  <p>Vertical sorting (alphabetical)</p>
  
  <pre><code>* Ash      * Date    * Grape
  * Beech    * Elm     * Hawthorn
  * Cedar    * Fir     * Ivy
  </code></pre>
  
  <p>Vertical sorting (numeric)</p>
  
  <pre><code>1. Ash      4. Date    7. Grape
  2. Beech    5. Elm     8. Hawthorn
  3. Cedar    6. Fir     9. Ivy 
  </code></pre>
  
  <p>Vertical sorting is the default behavior of many of the .Net web multi-column list controls (such as CheckBoxList).</p>
  
  <p>I researched the topic looking at the usual document formatting standards that I used in college (APA, MLA, Chicago), but I have found nothing related to multi-column lists.</p>
  
  <p>Are any actual arguments or document format standards/guidelines/rules for specifying the sort direction of multi-column lists?</p>