[css-align] Fix some markup errors.

Author: fantasai

css-align/Overview.bs

@@ -1449,7 +1449,7 @@ Determining the Baselines of a Box</h2>
 	for a given axis
 	are a set of baselines (alphabetic, central, etc.)
 	nominally associated with the first (last) line of text within the box.
-	The <a>alignment baseline</a> is one of these,
+	The <dfn export>alignment baseline</dfn> is one of these,
 	usually the dominant baseline associated with the <a>shared alignment context</a>.
 	(See the 'dominant-baseline' and 'alignment-baseline' properties in [[CSS-INLINE-3]].)
 
@@ -1582,7 +1582,7 @@ Baseline Alignment Terminology</h3>
 	exactly as for replaced elements and other boxes that have no <a>natural baseline</a>.
 
 
-	Boxes <dfn lt="shared alignment context|alignment context" export>share an alignment context</dfn> along a particular axis when they are:
+	Boxes share an <dfn lt="shared alignment context|alignment context" export>alignment context</dfn> along a particular axis when they are:
 
 	<ul>
 		<li>table cells in the same row, along the table's row (inline) axis