diff --git a/output_html.py b/output_html.py
index 90d62bb..0e980f9 100644
--- a/output_html.py
+++ b/output_html.py
@@ -8,14 +8,26 @@ def build_rows_depth_first(node, rows, leaf_count=0):
     for child in sorted(node.children, key=lambda x: x.height, reverse=True):
         leaf_count = build_rows_depth_first(child, rows, leaf_count)
 
+    colspan = 0
+    if node.siblings:
+        max_sibling_height = max([s.height for s in node.siblings])
+
+        if max_sibling_height > node.height:
+            colspan = max_sibling_height - node.height + 1
+
     if node.is_leaf:
         cur_row = leaf_count
-        rows[cur_row].append(f'<td>{node.name}</td>')
+        rows[cur_row].append(f'<th>{node.name}</th>')
+
+        if colspan > 1:
+            rows[cur_row].append(f'<td colspan="{colspan-1}"></td>')
+
         leaf_count += 1
+
     else:
         child_leaves = len(node.leaves)
         cur_row = leaf_count - child_leaves
-        rows[cur_row].append(f'<td rowspan="{child_leaves}" title="{node.description}">{node.name}</td>')
+        rows[cur_row].append(f"<td rowspan='{child_leaves}' colspan='{colspan}' title='{node.description}'>{node.name}</td>")
 
     return leaf_count
 
@@ -34,8 +46,12 @@ for i in range(len(root.leaves)):
 
 build_rows_depth_first(root, output_rows)
 
+print("<table cellspacing='0'>")
+
 for row in output_rows:
     print("<tr>")
     for cell in row:
         print(f"  {cell}")
     print("</tr>")
+
+print("</table>")