Adjust header height for more space for anchors

Adjusted the space from the header to the conent
to allow anchor links to be seen and not hidden
behind the header. More space is given to account
for different behaviour between Firefox and Chrome.

source/mahara/static/mahara.css_t

@@ -456,6 +456,15 @@ a.incognito:hover {
   color: #000000;
 }
 
+/* -- To show anchor links below header-------------------------------------- */
+
+:target {
+  display: block;
+  position: relative;
+  top: -120px;
+  visibility: hidden;
+}
+
 /* -- Buttons --------------------------------------------------------------- */
 .btn,
 .btn-default {