Minor tweaks to layout

Change-Id: I82fcf6cf1f50a51e75a1e3a162a118f51db98b99
diff --git a/visualisation/visualisation.py b/visualisation/visualisation.py
index 3f3462b..34bb389 100644
--- a/visualisation/visualisation.py
+++ b/visualisation/visualisation.py
@@ -49,7 +49,6 @@
     """ Cache for graphics state, to avoid having to recalculate every
         query too many times. """
     last_update = None
-    max_width = 0
     graphics = {}
 
     def __init__(self):
@@ -222,7 +221,7 @@
         page.append('.content {')
         page.append('	 position:relative;')
         page.append('    padding-top: 10px;')
-        page.append('	 width: %dpx;' % cache.max_width)
+        page.append('	 width: 80%;')
         page.append('	 max-width:80%;')
         page.append('	 margin-left: 21%;')
         page.append('    margin-top: 50px;')
@@ -289,7 +288,7 @@
         page.append('    text-indent: 0;')
         page.append('}')
         page.append('area + span {')
-        page.append('    position: fixed;')
+        page.append('    position: absolute;')
         page.append('    margin-left: -9999em;')
         page.append('    background: #00FFFF;')
         page.append('}')
@@ -311,7 +310,8 @@
         page.append('}')
         self.wfile.write('\r\n'.join(page))
 
-    # Send a graphic from our cache
+    # Generate a PNG showing the layout of switches/port/trunks for a
+    # specific VLAN
     def send_graphic(self):
         vlan_id = 0
         vlan_re = re.compile(r'^/images/vlan/(\d+).png$')