[css-display] Clarify that block/inline/run-in only affect flow layout. #1175

Author: fantasai

css-display/Overview.bs

@@ -281,15 +281,18 @@ Outer Display Roles for Flow Layout: the ''block'', ''inline'', and ''run-in'' k
 	<dl dfn-type="value" dfn-for="display, <display-outside>">
 		<dt><dfn>block</dfn>
 		<dd>
-			The element generates a <dfn dfn for>block-level box</dfn>. [[!CSS2]]
+			The element generates a <dfn dfn for>block-level box</dfn>
+			when placed in <a>flow layout</a>. [[!CSS2]]
 
 		<dt><dfn>inline</dfn>
 		<dd>
-			The element generates an <dfn dfn for>inline-level box</dfn>. [[!CSS2]]
+			The element generates an <dfn dfn for>inline-level box</dfn>
+			when placed in <a>flow layout</a>. [[!CSS2]]
 
 		<dt><dfn>run-in</dfn>
 		<dd>
-			The element generates a <a>run-in box</a>.
+			The element generates a <a>run-in box</a>
+			when placed in <a>flow layout</a>.
 			Run-in elements act like inlines or blocks,
 			depending on the surrounding elements.
 			See [[#run-in-layout]] for details.