Use l-box instead of margin

src/views/index.ecr

@@ -7,7 +7,7 @@
 <% slice.each do |video| %>
     <% player_response = JSON.parse(video.info["player_response"]) %>
     <div class="pure-u-1 pure-u-md-1-4">
-        <div style="margin:1em;">
+        <div class="l-box">
             <a style="width:100%;" href="/watch?v=<%= video.id %>">
                 <img style="width:100%;" src="<%= player_response["videoDetails"]["thumbnail"]["thumbnails"][0]["url"] %>"/>
                 <p><%= video.title %></p>