[css-inline-3] Clarify that initial letters are in-flow. #743

Author: fantasai

css-inline-3/Overview.bs

@@ -473,7 +473,8 @@ Creating Initial Letters: the 'initial-letter' property</h3>
 	See GitHub issue <a href="https://github.com/w3c/csswg-drafts/issues/862">862</a>.
 
 	An <dfn lt="initial letter | initial letter box">initial letter</dfn> is
-	a box to which 'initial-letter' applies and is not ''initial-letter/normal'':
+	an <a>in-flow</a> box
+	to which 'initial-letter' applies and is not ''initial-letter/normal'';
 	this triggers the special layout considerations described below.
 
 	<div class="example">