more correct wording for required properties

Author: fantasai

css3-page/Overview.html

@@ -3213,9 +3213,9 @@ <h3 class=no-num id=properties>Properties that apply within the page
      context</h3>
 
     <p>The following CSS 2.1 <a href="#CSS21"
-     rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> properties <em
-     class=RFC2119>MUST</em> be supported within an @page rule by conforming
-     implementations:</p>
+     rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> properties apply to the
+     page box. Conforming user agents must support all of these properties as
+     applied to the page box.</p>
 
     <table class=property-list>
      <tbody>
@@ -3416,13 +3416,17 @@ <h3 class=no-num id=properties>Properties that apply within the page
         href="/TR/CSS21/visufx.html#visibility">visibility</a>
     </table>
 
+    <p>Properties that apply to the margin boxes can also be set within the
+     page context: if inheritable or explicitly inherited (with the
+     <code>inherit</code> keyword), they will inherit to the margin boxes.</p>
+
     <h3 class=no-num id=properties0>Properties that apply within the margin
      contexts</h3>
 
     <p>The following CSS 2.1 <a href="#CSS21"
-     rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> properties <em
-     class=RFC2119>MUST</em> be supported by conforming implementations
-     within an @margin-box rule:</p>
+     rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a> properties apply to margin
+     boxes. Conforming user agents must support all of these properties
+     (except for <code>z-index</code>, which is optional).</p>
 
     <table class=property-list>
      <tbody>

css3-page/Overview.src.html

@@ -2255,8 +2255,9 @@ <h2 class="no-num" id="properties-list">Appendix A: Full List of Properties</h2>
 
 <h3 class="no-num">Properties that apply within the page context</h3>
 
-<p>The following CSS 2.1 [[!CSS21]] properties <em class="RFC2119">MUST</em> be
-supported within an @page rule by conforming implementations:</p>
+<p>The following CSS 2.1 [[!CSS21]] properties apply to the page box.
+Conforming user agents must support all of these properties as applied
+to the page box.</p>
 
 <table class="property-list">
   <tbody>
@@ -2334,10 +2335,16 @@ <h3 class="no-num">Properties that apply within the page context</h3>
     <tr><td colspan="2"><a href="/TR/CSS21/visufx.html#visibility">visibility</a>
 </table>
 
+<p>Properties that apply to the margin boxes can also be set within
+the page context: if inheritable or explicitly inherited (with the
+<code>inherit</code> keyword), they will inherit to the margin boxes.</p>
+
 <h3 class="no-num">Properties that apply within the margin contexts</h3>
 
-<p>The following CSS 2.1 [[!CSS21]] properties <em class="RFC2119">MUST</em> be
-supported by conforming implementations within an @margin-box rule:</p>
+<p>The following CSS 2.1 [[!CSS21]] properties apply to margin boxes.
+Conforming user agents must support all of these properties (except for
+<code>z-index</code>, which is optional).</p>
+
 <table class="property-list">
   <tbody>
     <tr><td rowspan="6"><a href="/TR/CSS21/colors.html#background-properties">background properties</a>