Added missing vendor prefixes

assets/css/screen.css

@@ -1441,6 +1441,8 @@ body:not(.post-template) .post-title {
 /* if there are two posts without covers, put a border between them */
 .read-next-story.no-cover + .read-next-story.no-cover {
     border-left: rgba(0,0,100,0.04) 1px solid;
+    -webkit-box-sizing: border-box;
+    -moz-box-sizing: border-box;
     box-sizing: border-box;
 }