Index: wp-content/themes/twentythirteen/style.css
===================================================================
--- wp-content/themes/twentythirteen/style.css	(revision 23488)
+++ wp-content/themes/twentythirteen/style.css	(working copy)
@@ -775,10 +775,6 @@
  */
 .site {
 	background-color: #fff;
-	border-left: 1px solid #f2f2f2;
-	border-right: 1px solid #f2f2f2;
-	margin: 0 auto;
-	max-width: 1600px;
 	width: 100%;
 }
 
@@ -2658,9 +2654,13 @@
 	}
 }
 
-@media (max-width: 1599px) {
+@media (min-width: 1600px) {
 	.site {
-		border: 0;
+		border-left: 1px solid #f2f2f2;
+		border-right: 1px solid #f2f2f2;
+		max-width: 1600px;
+		margin: 0 auto;
+		width: 99.8%;
 	}
 }