[css-page] markup typo

Author: tabatkins

css-page/Overview.bs

@@ -1890,9 +1890,11 @@ Crop and Registration Marks: the 'marks' property</h3>
 
 	<dl dfn-type=value dfn-for="@page/marks">
 		<dt><dfn>none</dfn>
+		<dd>
 			Specifies that neither crop marks nor registration marks should be printed:
 			the area outside the <a>bleed area</a> will be completely blank.
 		<dt><dfn>crop</dfn>
+		<dd>
 			Specifies that crop marks should be printed.
 			These are typically short lines outside the page box
 			that are effectively extensions of the page box's four edges,