Skip @context key.
--- a/spec/latest/json-ld-api/index.html	Tue Feb 12 16:04:26 2013 -0500
+++ b/spec/latest/json-ld-api/index.html	Tue Feb 12 16:11:12 2013 -0500
@@ -1445,6 +1445,10 @@
         ordered lexicographically by <em>key</em>:
         <ol class="algorithm">
           <li>
+            If <em>key</em> equals <code>@context</code>, continue to
+            the next <em>key</em>.
+          </li>
+          <li>
             If <em>key</em> is mapped to a <tref>property generator</tref>
             in <tref>active context</tref>, set <em>expanded property</em>
             to an array containing its <tref title="IRI">IRIs</tref>.