From 984a13e45b7481b415101772e344b8f9a668ea0b Mon Sep 17 00:00:00 2001
From: "SangKa.Z" <sangka23@163.com>
Date: Fri, 2 Mar 2018 21:52:58 +0800
Subject: [PATCH] docs(aio): fix table header (#22553)

PR Close #22553
---
 aio/content/guide/comparing-observables.md | 28 ++++++++++++----------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/aio/content/guide/comparing-observables.md b/aio/content/guide/comparing-observables.md
index 9cb663cd56..5e7b9b0ca4 100644
--- a/aio/content/guide/comparing-observables.md
+++ b/aio/content/guide/comparing-observables.md
@@ -89,11 +89,11 @@ promise.then(() => {
 The following code snippets illustrate how the same kind of operation is defined using observables and promises.
 
 <table>
-  <th>
-    <td>Operation</td>
-    <td>Observable</td>
-    <td>Promise</td>
-  </th>
+  <tr>
+    <th>Operation</th>
+    <th>Observable</th>
+    <th>Promise</th>
+  </tr>
   <tr>
     <td>Creation</td>
     <td>
@@ -141,10 +141,11 @@ Using observables to handle events and asynchronous operations can have the adva
 Here are some code samples that illustrate how the same kind of operation is defined using observables and the events API.
 
 <table>
-  <th>
-    <td>Observable</td>
-    <td>Events API</td>
-  </th>
+  <tr>
+    <th></th>
+    <th>Observable</th>
+    <th>Events API</th>
+  </tr>
   <tr>
     <td>Creation & cancellation</td>
     <td>
@@ -203,10 +204,11 @@ button.removeEventListener(‘click’, handler);
 An observable produces values over time. An array is created as a static set of values. In a sense, observables are asynchronous where arrays are synchronous. In the following examples, ➞ implies asynchronous value delivery.
 
 <table>
-  <th>
-    <td>Observable</td>
-    <td>Array</td>
-  </th>
+  <tr>
+    <th></th>
+    <th>Observable</th>
+    <th>Array</th>
+  </tr>
   <tr>
     <td>Given</td>
     <td>