Editorial fixes

Closes #4

graphics-aria/img/nested-figures.html

@@ -56,9 +56,9 @@
         <svg id="fig1A" class="nested-figure" role="figure"
              aria-labelledby="fig1-caption, fig1A-caption">
             <linearGradient id="repeat" x2="25%" spreadMethod="repeat">
-                <stop offset="0"     stop-color="black" />
+                <stop offset="0"   stop-color="black" />
                 <stop offset="0.8" stop-color="white" />
-                <stop offset="1"     stop-color="black" />
+                <stop offset="1"   stop-color="black" />
             </linearGradient>
             <text id="fig1A-caption" class="caption" dy="1em"
                   >a) spreadMethod="repeat"</text>

graphics-aria/index.html

@@ -536,13 +536,15 @@ <h2>Definition of Roles</h2>
           A graphical object may itself have nested sub-components.
         </p>
         <p>
-          Container elements that instead represent a collection
-          of disconnected objects should instead be given the
-          <rref>group</rref> or <rref>list</rref> roles.
+          Container elements that represent a collection
+          of disconnected objects should be given the
+          <rref>group</rref> or <rref>list</rref> roles, instead.
           Grouping elements that do not have semantic meaning 
           and do not alter the semantic context provided by an ancestor
-          SHOULD NOT be given a role, 
-          which may be explicitly indicated 
+          (for example, a <code>div</code> or SVG <code>g</code>
+          that is only used for styling or layout)
+          SHOULD NOT be given a role. 
+          The lack of role may be explicitly indicated 
           with the role <rref>none</rref> or <rref>presentation</rref>.
         </p>
         <p>