We seem to have interop on not requiring whitespace here, both before { and before (, so go back to the CSS 2.1 way.

Author: dbaron

css3-conditional/Overview.html

@@ -492,7 +492,7 @@ <h2 id=at-media><span class=secno>5. </span>Media-specific style sheets:
    into:
 
   <pre>media
-  : MEDIA_SYM S+ media_query_list group_rule_body
+  : MEDIA_SYM S* media_query_list group_rule_body
   ;</pre>
 
   <p>where the <code>group_rule_body</code> production is defined in this
@@ -502,10 +502,6 @@ <h2 id=at-media><span class=secno>5. </span>Media-specific style sheets:
    href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a> (<a
    href="#CSS21" rel=biblioentry>[CSS21]<!--{{!CSS21}}--></a>, Appendix G).
 
-  <p class=issue>This changes the <code>S*</code> in CSS 2.1 into
-   <code>S+</code>. Is that correct? (Actually, probably not, since I think
-   "@media{" is valid.)
-
   <h2 id=at-supports><span class=secno>6. </span>Feature queries: the ‘<a
    href="#dfn-support"><code class=css>@supports</code></a>’ rule</h2>
 

css3-conditional/Overview.src.html

@@ -324,18 +324,14 @@ <h2 id="at-media">Media-specific style sheets:  the '@media' rule</h2>
 <a href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
 ([[!CSS21]], Appendix G) into:
 <pre>media
-  : MEDIA_SYM S+ media_query_list group_rule_body
+  : MEDIA_SYM S* media_query_list group_rule_body
   ;</pre>
 <p>where the <code>group_rule_body</code> production is defined in this
 specification, the <code>media_query_list</code> production is defined
 in [[!MEDIAQ]], and the others are defined in the <a
 href="http://www.w3.org/TR/CSS21/grammar.html">Grammar of CSS 2.1</a>
 ([[!CSS21]], Appendix G).
 
-<p class="issue">This changes the <code>S*</code> in CSS 2.1 into
-<code>S+</code>.  Is that correct?  (Actually, probably not, since
-I think "@media{" is valid.)</p>
-
 <h2 id="at-supports">Feature queries: the '@supports' rule</h2>
 
 <p>The <dfn>'@supports' rule</dfn> is a conditional group