[css-display] Clarify that inner display types are irrelevant for replaced elements

Author: fantasai

css-display/Overview.bs

@@ -122,8 +122,9 @@ Box Layout Modes: the 'display' property</h2>
 	which consists of the two basic qualities of how an element generates boxes:
 
 	* the <dfn export local-lt="inner">inner display type</dfn>,
-		which defines the kind of <a>formatting context</a> it generates,
+		which defines (if it a <a href="http://www.w3.org/TR/CSS2/conform.html#replaced-element">non-replaced element</a>) the kind of <a>formatting context</a> it generates,
 		dictating how its descendant boxes are laid out.
+		(The inner display of a <a href="http://www.w3.org/TR/CSS2/conform.html#replaced-element">replaced element</a> is outside the scope of CSS.)
 	* the <dfn export local-lt="outer">outer display type</dfn>,
 		which dictates how the box participates in its parent formatting context.
 
@@ -292,7 +293,8 @@ Outer Display Roles for Flow Layout: the ''block'', ''inline'', and ''run-in'' k
 Inner Display Layout Models: the ''flow'', ''flow-root'', ''table'', ''grid'', and ''ruby'' keywords</h3>
 
 	The <<display-inside>> keywords specify the element's <a>inner display type</a>,
-	which defines the type of formatting context that lays out its contents.
+	which defines the type of formatting context that lays out its contents
+	(assuming it is a <a href="http://www.w3.org/TR/CSS2/conform.html#replaced-element">non-replaced</a> element).
 	They are defined as follows:
 
 	<dl dfn-type="value" dfn-for="display, <display-inside>">