[css-values-4] Minor wording fixes to viewport units section.

Author: fantasai

css-values-4/Overview.bs

@@ -1839,7 +1839,7 @@ The Large, Small, and Dynamic Viewport Sizes</h5>
 			during the UI animation.
 			(It is recommended that UAs assume the fully-retracted size
 			for this duration.)
-		</dl>
+	</dl>
 
 	Whether the expansion/retraction of a particular interface
 	changes the sizes of all of the [=viewport-percentage lengths=]
@@ -1851,17 +1851,18 @@ The Large, Small, and Dynamic Viewport Sizes</h5>
 	However,
 	UAs <em>must</em> categorize as the latter
 	any changes in interface that happen as a result of scrolling
-	or other frequent actions that would disturb the user
+	or other frequent page interactions that would disturb the user
 	if they resulted in substantial layout changes.
 	Additionally,
 	UAs may have some dynamically-shown interfaces which intentionally overlay content
-	and do not cause any shifts in layout;
+	and do not cause any shifts in layout
+	(and therefore have no effect on any of the [=viewport-percentage lengths=];
 	typically on-screen keyboards will fit into this category.
 
 	For [=paged media=], the exact definition of the viewport-percentage lengths
 	is deferred to [[!CSS3PAGE]].
 	However, in the typical case of all pages being the same size,
-	they are sized relative to the [=page area=].
+	they are sized relative to the [=initial containing block=].
 
 	In all cases, scrollbars are assumed not to exist.
 	<span class='note'>Note however that the [=initial containing block=]'s size
@@ -1975,7 +1976,7 @@ The Various Viewport-relative Units</h5>
 	In situations where there is no root element
 	or it hasn't yet been styled
 	(such as when evaluating <a>media queries</a>),
-	the ''vi'' and ''vb'' units use the initial value of the 'writing-mode' property
+	the ''*vi'' and ''*vb'' units use the initial value of the 'writing-mode' property
 	to determine which axis they correspond to.
 
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