refine the content

@@ -14,15 +14,14 @@ For the wiki for SRS/3.0, please read [Chinese][srs_CN] or [English][srs_EN].
 ## Content
 
 * [About](#about)
-* [Usage](#usage)
+* [Product](#product)
+  * [Usage](#usage)
   * [Wiki for v3.0](#srs-30-wiki)
+  * [v3.0 changes](#v3-changes)
   * [Wiki for v2.0](#srs-20-wiki)
+  * [v2.0 changes](#v2-changes)
   * [Wiki for v1.0](#srs-10-wiki)
-* [Product](#product)
-  * [History](#history)
-    * [v3.0 changes](#v3-changes)
-    * [v2.0 changes](#v2-changes)
-    * [v1.0 changes](#v1-changes)
+  * [v1.0 changes](#v1-changes)
   * [Releases](#releases)
   * [Features](#features)
   * [Compare](#compare)
@@ -68,7 +67,11 @@ and session based log, linux service script and install script.
 
 Enjoy it!
 
-## Usage
+## Product
+
+The `usage`, `wiki`, `changes`, `features`, `compare`, `release` and `performance` of SRS.
+
+### Usage
 
 <strong>Step 1:</strong> Get SRS.
 <strong>Download slow? Please use [mirrors](#mirrors) for SRS.</strong>
@@ -109,33 +112,25 @@ cd srs/trunk
 * Usage: Solution using SRS?([CN][v1_CN_Sample], [EN][v1_EN_Sample])
 * Usage: Why SRS?([CN][v1_CN_Product], [EN][v1_EN_Product])
 
-### Wiki
-
-#### SRS 1.0 wiki
+### SRS 1.0 wiki
 
 Please select your language:
 * [SRS 1.0 English][v1_EN_Home]
 * [SRS 1.0 Chinese][v1_CN_Home]
 
-#### SRS 2.0 wiki
+### SRS 2.0 wiki
 
 Please select your language:
 * [SRS 2.0 English][v2_EN_Home]
 * [SRS 2.0 Chinese][v2_CN_Home]
 
-#### SRS 3.0 wiki
+### SRS 3.0 wiki
 
 Please select your language:
 * [SRS 3.0 English][v3_EN_Home]
 * [SRS 3.0 Chinese][v3_CN_Home]
 
-## Product
-
-The changes `history`, `features`, `compare`, `release` and `performance` of SRS.
-
-### History
-
-#### V3 changes
+### V3 changes
 
 * v3.0, 2016-12-15, fix #717, #691, http api/static/stream support cors. 3.0.9
 * v3.0, 2016-12-08, support log rotate signal SIGUSR1. 3.0.8
@@ -151,7 +146,7 @@ The changes `history`, `features`, `compare`, `release` and `performance` of SRS
 * v3.0, 2015-08-28, fix [#471][bug #471], api response the width and height. 3.0.2
 * v3.0, 2015-08-25, fix [#367][bug #367], support nginx-rtmp exec. 3.0.1
 
-#### V2 changes
+### V2 changes
 
 * <strong>v2.0, 2016-12-13, [2.0 beta3(2.0.223)][r2.0b3] released. 86685 lines.</strong>
 * <strong>v2.0, 2016-11-09, [2.0 beta2(2.0.221)][r2.0b2] released. 86691 lines.</strong>
@@ -293,7 +288,7 @@ The changes `history`, `features`, `compare`, `release` and `performance` of SRS
 * v2.0, 2014-10-18, remove supports for OSX(darwin). 2.0.1.
 * v2.0, 2014-10-16, revert github srs README to English. 2.0.0.
 
-#### V1 changes
+### V1 changes
 
 * <strong>v1.0, 2014-12-05, [1.0 release(1.0.10)][r1.0r0] released. 59391 lines.</strong>
 * <strong>v1.0, 2014-10-09, [1.0 beta(1.0.0)][r1.0b0] released. 59316 lines.</strong>