Small style fixes

- write site's HTTP 400 in a single line
- add an space at the end of the query parameter in site's random/tag in
  order to start writing after a space on focus
- use <%= ... %> instead of manually escaping a smiley

templates/media.html.ep

@@ -4,7 +4,7 @@
 
 <div class="media-metadata">
 % if ($tags->@* == 0) {
-    <p>Non tags yet. &gt;_&lt;</p>
+    <p>Non tags yet. <%= ">_<'" %></p>
 % } else {
   <dl>
 %   for my $entry (tags_by_kind $tags) {