Update index.html

Author: marcoscaceres

index.html

@@ -473,7 +473,7 @@ <h3>
             "<dfn data-dfn-for="text-direction">auto</dfn>" (default)
           </dt>
           <dd>
-            <p>Direction determined from content.</p>
+            <p>Direction determined from content using the first-strong part of the [[BIDI]] algorithm.</p>
             <aside class="note">
               <p>
                 An actual direction value such as `rtl` or `ltr` is preferred to relying on `auto`.