Adjust caching and accessibility

css/archive_tree.css

@@ -9,9 +9,13 @@
 .archive-tree-year {
   font-weight: normal;
 }
+.archive-tree-month-list {
+    margin: 0;
+    padding-left: 2em;
+}
 .archive-tree-month {
-  margin-left: 2em;
-  padding-left: 0.5em;
+  margin-left: 0;
+  padding-left: 0;
   border-left: 2px solid #ccc;
   display: block;
 }