w3c
diff --git a/‎css-text-3/Overview.bs‎
Lines changed: 13 additions & 8 deletions b/‎css-text-3/Overview.bs‎
Lines changed: 13 additions & 8 deletions
@@ -165,12 +165,18 @@ Languages and Typesetting</h3>
     the element is declared to be in, according to the rules of the
     <a href="https://www.w3.org/TR/CSS21/conform.html#doclanguage">document language</a>.
     For example, the rules for determining the <a>content language</a> of an HTML
-    element use the <code>lang</code> attribute and are defined in [[HTML5]],
+    are <a href="https://html.spec.whatwg.org/multipage/dom.html#language">defined</a> in [[HTML]],
     and the rules for determining the <a>content language</a> of an XML element use
-    the <code>xml:lang</code> attribute and are
-    <a href="https://www.w3.org/TR/REC-xml/#sec-lang-tag">defined</a> in [[XML10]].
+    are <a href="https://www.w3.org/TR/REC-xml/#sec-lang-tag">defined</a> in [[XML10]].
     Note that it is possible for the <a>content language</a> of an element
-    to be unknown.
+    to be unknown--
+    e.g. untagged content,
+    or content in a <a>document language</a> that does not have a language-tagging facility
+    is considered to have an unknown <a>content language</a>.
+
+    Note: Authors can tag content using the global <code>lang</code> attribute in HTML,
+    the universal <code>xml:lang</code> attribute in XML,
+    and the HTTP <code>Content-Language</code> header for content served over HTTP.
 
     Language and writing system conventions can affect
     line breaking, hyphenation, justification, glyph selection,
@@ -1178,16 +1184,15 @@ Line Breaking Details</h3>
 
     <p>Correct automatic hyphenation requires a hyphenation resource
       appropriate to the language of the text being broken.
-      The UA is therefore only required to automatically hyphenate text
+      The UA must therefore only automatically hyphenate text
       for which the <a>content language</a> is known
       and for which it has an appropriate hyphenation resource.
 
     <p class="advisement">
       Authors should correctly tag their content’s <a lt="content language">language</a>
-      (e.g. using the HTML ''lang'' attribute)
+      (e.g. using the HTML <code>lang</code> attribute
+      or the HTTP <code>Content-Language</code> header)
       in order to obtain correct automatic hyphenation.
-      UAs may refuse to automatically hyphenate untagged content
-      regardless of the 'hyphens' property value.
 
     <p>When shaping scripts such as Arabic are allowed to break within words
       due to hyphenation,