[css-text-3] Tweak example: markup, wording, source formatting

Author: fantasai

css-text-3/Overview.bs

@@ -1046,11 +1046,14 @@ Line Breaking Details</h3>
         background: white;
       }
       </style>
-      <p>Japanese is usually laid out to allow line breaks within words.
-      However, it is sometimes preferred to suppress these wrapping opportunities and to only allow wrapping at the end of certain sentence fragments.
-      This is most commonly done in very short pieces of text, such as headings, table or figure captions.
-
-      This can be achieved by marking the allowed wrapping points with <{wbr}> or U+200B ZERO WIDTH SPACE,
+      <p>Japanese is usually typeset allowing line breaks within words.
+      However, it is sometimes preferred to suppress these wrapping opportunities
+      and to only allow wrapping at the end of certain sentence fragments.
+      This is most commonly done in very short pieces of text,
+      such as headings and table or figure captions.
+
+      This can be achieved by marking the allowed wrapping points
+      with <{wbr}> or U+200B ZERO WIDTH SPACE,
       and suppressing the other ones using ''word-break: keep-all''.
 
       For instance, the following markup can produce either of the renderings below,
@@ -1060,12 +1063,16 @@ Line Breaking Details</h3>
       </code></pre>
 
       <table class=data>
+      <colgroup span=1></colgroup>
+      <colgroup span=2></colgroup>
+      <thead>
       <tr>
         <td>
         <th><code highlight=css>h1 { word-break: normal }</code>
         <th><code highlight=css>h1 { word-break: keep-all }</code>
+      <tbody>
       <tr>
-        <th>Expected rendering
+        <th scope=row>Expected rendering
         <td>
           <pre lang=ja>
 	  窓ぎわのトットちゃ
@@ -1075,7 +1082,7 @@ Line Breaking Details</h3>
 	  窓ぎわの
 	  トットちゃん</pre>
       <tr>
-        <th>Result in your browser
+        <th scope=row>Result in your browser
         <td>
           <samp lang=ja>
           窓ぎわの<wbr>トットちゃん