Change css style sheets.

_sass/_base.scss

@@ -26,7 +26,7 @@ body {
     line-height: $base-line-height;
     font-weight: 300;
     color: $text-color;
-    background-color: $background-color;
+    background-color: white;
     -webkit-text-size-adjust: 100%;
 }
 
@@ -140,7 +140,8 @@ code {
     font-size: 15px;
     border: 1px solid $grey-color-light;
     border-radius: 3px;
-    background-color: #eef;
+    background-color: #f7f7f7;
+    font-family: Courier;
 }
 
 code {
@@ -149,7 +150,6 @@ code {
 
 pre {
     padding: 8px 12px;
-    overflow-x: scroll;
 
     > code {
         border: 0;