[css-ui-4] Minor rephasings and typo fixing

Author: frivoal

css-ui-4/Overview.bs

@@ -1791,7 +1791,7 @@ This specification introduces the 'appearance' property
 to provide some control over this behavior.
 In particular, using ''appearance: none'' allows authors
 to suppress the native style of form controls,
-so that CSS can be used to fully restyle them.
+so that CSS can be used to restyle them.
 
 <pre class="propdef">
 Name: appearance, -webkit-appearance
@@ -1840,7 +1840,7 @@ Animation type: discrete
 
 		Issue: On some elements, setting some properties inhibits ''appearance: auto''.
 		For instance, even if 'appearance' is ''appearance/auto'',
-		buttons lose they native appearance when a 'border' is set.
+		buttons lose their native appearance when a 'border' is set.
 		This is not in contradiction with this part of the spec,
 		since ''appearance: auto'' only means
 		UAs <em>may</em> use a native appearance,
@@ -1852,7 +1852,7 @@ Animation type: discrete
 	<dt><dfn>button</dfn>
 	<dd>
 		The element is rendered with the look and feel of a push button,
-		similar to the rendering of the [[HTML]] <{button}> element.
+		similar to the ''appearance: auto'' rendering of the [[HTML]] <{button}> element.
 
 		Issue: Are there some form controls or other replaced elements
 		on which this value should be a no&#x2011;op?