Another changes to MD theme

boards/static/css/md/base_page.css

@@ -51,10 +51,11 b' body {'
 
 .post, .dead_post, .archive_post, #posts-table {
     background: #333;
-    margin-top: 5px;
     padding: 10px;
     clear: left;
     word-wrap: break-word;
+    border-top: 1px solid #777;
+    border-bottom 1px solid #777;
 }
 
 .metadata {
@@ -242,6 +243,7 b' a:hover {'
 
 .thread {
     margin-bottom: 3ex;
+    margin-top: 1ex;
 }
 
 .post:target {
@@ -403,7 +405,3 b' pre {'
     margin: 0.2ex;
     padding: 0.1ex;
 }
-
-.post_preview {
-    border: solid 1px #888;
-}