Stylesheet: Fix the target link for section headers

The earlier fix resulted in section headers to
not be displayed any more.

source/mahara/static/mahara.css_t

@@ -465,6 +465,19 @@ a.incognito:hover {
   visibility: hidden;
 }
 
+.section:target {
+  position: static;
+  visibility: visible;
+  top: 0;
+} 
+
+.section::before {
+  content: '';
+  display: block;
+  height: 120px
+  margin-top: -120px;
+  visibility: hidden;
+}
 /* -- Buttons --------------------------------------------------------------- */
 .btn,
 .btn-default {