Apply suggestions from code review

Co-authored-by: Tab Atkins Jr. <jackalmage@gmail.com>

Author: noamr

css-syntax-3/Overview.bs

@@ -2121,8 +2121,8 @@ Parse A Comma-Separated List According To A CSS Grammar</h4>
 Parse a stylesheet</h4>
 
 	<div algorithm>
-		To <dfn export>parse a stylesheet</dfn> from an |input| given [=/url=] or Null |location|
-		(default null):
+		To <dfn export>parse a stylesheet</dfn> from an |input| 
+		given an optional [=/url=] |location|:
 
 		<ol>
 			<li>
@@ -2135,7 +2135,7 @@ Parse a stylesheet</h4>
 				and set |input| to the result.
 
 			<li>
-				Create a new stylesheet, with its <a spec=cssom>location</a> set to |location|.
+				Create a new stylesheet, with its <a spec=cssom>location</a> set to |location| (or null, if |location| was not passed).
 
 			<li>
 				<a>Consume a list of rules</a> from |input|,