diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/Page.java b/webmagic-core/src/main/java/us/codecraft/webmagic/Page.java
index 2516dd1..afdf232 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/Page.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/Page.java
@@ -9,13 +9,13 @@ import java.util.List;
 
 /**
  *
- * Object storing extracted result and urls to be crawled.<br>
+ * Object storing extracted result and urls to fetch.<br>
  * Main method：                                               <br>
  * {@link #getUrl()} get url of current page                   <br>
  * {@link #getHtml()}  get content of current page                 <br>
  * {@link #putField(String, Object)}  save extracted result            <br>
  * {@link #getResultItems()} get extract results to be used in {@link us.codecraft.webmagic.pipeline.Pipeline}<br>
- * {@link #addTargetRequests(java.util.List)} {@link #addTargetRequest(String)} add urls to crawl                 <br>
+ * {@link #addTargetRequests(java.util.List)} {@link #addTargetRequest(String)} add urls to fetch                 <br>
  *
  * @author code4crafter@gmail.com <br>
  * @since 0.1.0
@@ -71,7 +71,7 @@ public class Page {
     }
 
     /**
-     * add urls to crawl
+     * add urls to fetch
      *
      * @param requests
      */
@@ -88,7 +88,7 @@ public class Page {
     }
 
     /**
-     * add url to crawl
+     * add url to fetch
      *
      * @param requestString
      */
@@ -103,7 +103,7 @@ public class Page {
     }
 
     /**
-     * add requests to crawl
+     * add requests to fetch
      *
      * @param request
      */
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/Downloader.java b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/Downloader.java
index 9a7f59a..ec74950 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/Downloader.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/Downloader.java
@@ -5,16 +5,17 @@ import us.codecraft.webmagic.Request;
 import us.codecraft.webmagic.Task;
 
 /**
- * Downloader是webmagic下载页面的接口。webmagic默认使用了HttpComponent作为下载器，一般情况，你无需自己实现这个接口。<br>
+ * Downloader is the part that downloads web pages and store in Page object. <br>
+ * Downloader has {@link #setThread(int)} method because downloader is always the bottleneck of a crawler,
+ * there are always some mechanisms such as pooling in downloader, and pool size is related to thread numbers.
  *
  * @author code4crafter@gmail.com <br>
- *         Date: 13-4-21
- *         Time: 下午12:14
+ * @since 0.1.0
  */
 public interface Downloader {
 
     /**
-     * 下载页面，并保存信息到Page对象中。
+     * Downloads web pages and store in Page object.
      *
      * @param request
      * @param task
@@ -23,10 +24,8 @@ public interface Downloader {
     public Page download(Request request, Task task);
 
     /**
-     * 设置线程数，多线程程序一般需要Downloader支持<br>
-     * 如果不考虑多线程的可以不实现这个方法<br>
-     *
-     * @param thread 线程数量
+     * Tell the downloader how many threads the spider used.
+     * @param threadNum number of threads
      */
-    public void setThread(int thread);
+    public void setThread(int threadNum);
 }
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientDownloader.java b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientDownloader.java
index fd68021..7563410 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientDownloader.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientDownloader.java
@@ -4,6 +4,7 @@ import org.apache.commons.io.IOUtils;
 import org.apache.http.Header;
 import org.apache.http.HeaderElement;
 import org.apache.http.HttpResponse;
+import org.apache.http.annotation.ThreadSafe;
 import org.apache.http.client.HttpClient;
 import org.apache.http.client.entity.GzipDecompressingEntity;
 import org.apache.http.client.methods.HttpGet;
@@ -22,12 +23,12 @@ import java.util.Set;
 
 
 /**
- * 封装了HttpClient的下载器。已实现指定次数重试、处理gzip、自定义UA/cookie等功能。<br>
+ * The http downloader based on HttpClient.
  *
  * @author code4crafter@gmail.com <br>
- *         Date: 13-4-21
- *         Time: 下午12:15
+ * @since 0.1.0
  */
+@ThreadSafe
 public class HttpClientDownloader implements Downloader {
 
     private Logger logger = Logger.getLogger(getClass());
@@ -35,14 +36,14 @@ public class HttpClientDownloader implements Downloader {
     private int poolSize = 1;
 
     /**
-     * 直接下载页面的简便方法
+     * A simple method to download a url.
      *
      * @param url
      * @return html
      */
     public Html download(String url) {
         Page page = download(new Request(url), null);
-        return (Html)page.getHtml();
+        return (Html) page.getHtml();
     }
 
     @Override
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientPool.java b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientPool.java
index c6e2652..f2fffad 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientPool.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientPool.java
@@ -20,8 +20,7 @@ import java.util.Map;
 
 /**
  * @author code4crafter@gmail.com <br>
- *         Date: 13-4-21
- *         Time: 下午12:29
+ * @since 0.1.0
  */
 public class HttpClientPool {
 
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/package.html b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/package.html
index cae5560..719abd9 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/package.html
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/downloader/package.html
@@ -1,5 +1,5 @@
 <html>
 	<body>
-包含了页面下载的接口Downloader和实现类HttpClientDownloader，该实现类封装了HttpComponent库。
+Downloader is the part that downloads web pages and store in Page object.
 	</body>
 </html>
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/ConsolePipeline.java b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/ConsolePipeline.java
index e1648fe..888e455 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/ConsolePipeline.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/ConsolePipeline.java
@@ -6,11 +6,11 @@ import us.codecraft.webmagic.Task;
 import java.util.Map;
 
 /**
- * 命令行输出抽取结果。可用于测试。<br>
+ * Write results in console.<br>
+ * Usually used in test.
  *
  * @author code4crafter@gmail.com <br>
- *         Date: 13-4-21
- *         Time: 下午1:45
+ * @since 0.1.0
  */
 public class ConsolePipeline implements Pipeline {
 
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/FilePipeline.java b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/FilePipeline.java
index 9c88ba9..04709f2 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/FilePipeline.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/FilePipeline.java
@@ -1,6 +1,7 @@
 package us.codecraft.webmagic.pipeline;
 
 import org.apache.commons.codec.digest.DigestUtils;
+import org.apache.http.annotation.ThreadSafe;
 import org.apache.log4j.Logger;
 import us.codecraft.webmagic.ResultItems;
 import us.codecraft.webmagic.Task;
@@ -12,28 +13,23 @@ import java.io.PrintWriter;
 import java.util.Map;
 
 /**
- * 持久化到文件的接口。
+ * Store results in files.<br>
  *
  * @author code4crafter@gmail.com <br>
- *         Date: 13-4-21
- *         Time: 下午6:28
+ * @since 0.1.0
  */
-public class FilePipeline extends FilePersistentBase implements Pipeline  {
+@ThreadSafe
+public class FilePipeline extends FilePersistentBase implements Pipeline {
 
     private Logger logger = Logger.getLogger(getClass());
 
     /**
-     * 新建一个FilePipeline，使用默认保存路径"/data/webmagic/"
+     * create a FilePipeline with default path"/data/webmagic/"
      */
     public FilePipeline() {
         setPath("/data/webmagic/");
     }
 
-    /**
-     * 新建一个FilePipeline
-     *
-     * @param path 文件保存路径
-     */
     public FilePipeline(String path) {
         setPath(path);
     }
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/Pipeline.java b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/Pipeline.java
index 595a8e8..af2ed8c 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/Pipeline.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/Pipeline.java
@@ -4,12 +4,21 @@ import us.codecraft.webmagic.ResultItems;
 import us.codecraft.webmagic.Task;
 
 /**
- * Pipeline是数据离线处理和持久化的接口。通过实现Pipeline以实现不同的持久化方式(例如保存到数据库)。
+ * Pipeline is the persistent and offline process part of crawler.<br>
+ * The interface Pipeline can be implemented to customize ways of persistent.
+ *
  * @author code4crafter@gmail.com <br>
- * Date: 13-4-21
- * Time: 下午1:39
+ * @since 0.1.0
+ * @see ConsolePipeline
+ * @see FilePipeline
  */
 public interface Pipeline {
 
-    public void process(ResultItems resultItems,Task task);
+    /**
+     * Process extracted results.
+     *
+     * @param resultItems
+     * @param task
+     */
+    public void process(ResultItems resultItems, Task task);
 }
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/package.html b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/package.html
index 498183e..6b0fcee 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/package.html
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/pipeline/package.html
@@ -1,5 +1,5 @@
 <html>
 	<body>
-包含了处理页面抽取结果的接口Pipeline和它的几个实现类。
+Pipeline is the persistent and offline process part of crawler.
 	</body>
 </html>
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/processor/PageProcessor.java b/webmagic-core/src/main/java/us/codecraft/webmagic/processor/PageProcessor.java
index 3963d08..e0bb623 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/processor/PageProcessor.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/processor/PageProcessor.java
@@ -4,23 +4,33 @@ import us.codecraft.webmagic.Page;
 import us.codecraft.webmagic.Site;
 
 /**
- * 定制爬虫的核心接口。通过实现PageProcessor可以实现一个定制的爬虫。<br>
- *     extends the class to implements various spiders.<br>
+ * Interface to be implemented to customize a crawler.<br>
+ * <br>
+ * In PageProcessor, you can customize:
+ * <p/>
+ * start urls and other settings in {@link Site}<br>
+ * how the urls to fetch are detected               <br>
+ * how the data are extracted and stored             <br>
+ *
  * @author code4crafter@gmail.com <br>
- * Date: 13-4-21
- * Time: 上午11:42
+ * @see Site
+ * @see Page
+ * @since 0.1.0
  */
 public interface PageProcessor {
 
     /**
-     * 定义如何处理页面，包括链接提取、内容抽取等。
+     * process the page, extract urls to fetch, extract the data and store
+     *
      * @param page
      */
     public void process(Page page);
 
     /**
-     * 定义任务一些配置信息，例如开始链接、抓取间隔、自定义cookie、自定义UA等。
+     * get the site settings
+     *
      * @return site
+     * @see Site
      */
     public Site getSite();
 }
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/processor/SimplePageProcessor.java b/webmagic-core/src/main/java/us/codecraft/webmagic/processor/SimplePageProcessor.java
index 285a63d..a0572a9 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/processor/SimplePageProcessor.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/processor/SimplePageProcessor.java
@@ -7,10 +7,10 @@ import us.codecraft.webmagic.utils.UrlUtils;
 import java.util.List;
 
 /**
- * 非常简单的抽取器。链接抽取使用定义的通配符，并保存抽取整个内容到content字段。<br>
+ * A simple PageProcessor.
+ *
  * @author code4crafter@gmail.com <br>
- * Date: 13-4-22
- * Time: 下午9:15
+ * @since 0.1.0
  */
 public class SimplePageProcessor implements PageProcessor {
 
@@ -22,25 +22,25 @@ public class SimplePageProcessor implements PageProcessor {
         this.site = Site.me().addStartUrl(startUrl).
                 setDomain(UrlUtils.getDomain(startUrl));
         //compile "*" expression to regex
-        this.urlPattern = "("+urlPattern.replace(".","\\.").replace("*","[^\"'#]*")+")";
+        this.urlPattern = "(" + urlPattern.replace(".", "\\.").replace("*", "[^\"'#]*") + ")";
 
     }
 
     @Override
     public void process(Page page) {
         List<String> requests = page.getHtml().links().regex(urlPattern).all();
-        //调用page.addTargetRequests()方法添加待抓取链接
+        //add urls to fetch
         page.addTargetRequests(requests);
-        //xpath方式抽取
+        //extract by XPath
         page.putField("title", page.getHtml().xpath("//title"));
-        //sc表示使用Readability技术抽取正文
         page.putField("html", page.getHtml().toString());
+        //extract by Readability
         page.putField("content", page.getHtml().smartContent());
     }
 
     @Override
     public Site getSite() {
-        //定义抽取站点的相关参数
+        //settings
         return site;
     }
 }
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/processor/package.html b/webmagic-core/src/main/java/us/codecraft/webmagic/processor/package.html
index 47274a1..5ec7537 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/processor/package.html
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/processor/package.html
@@ -1,5 +1,5 @@
 <html>
 	<body>
-包含了封装页面处理逻辑的接口PageProcessor和一个实现类SimplePageProcessor。实现PageProcessor即可定制一个自己的爬虫。
+PageProcessor custom part of a crawler for specific site.
 	</body>
 </html>
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/QueueScheduler.java b/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/QueueScheduler.java
index 723b5f9..b263f91 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/QueueScheduler.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/QueueScheduler.java
@@ -1,5 +1,6 @@
 package us.codecraft.webmagic.scheduler;
 
+import org.apache.http.annotation.ThreadSafe;
 import org.apache.log4j.Logger;
 import us.codecraft.webmagic.Request;
 import us.codecraft.webmagic.Task;
@@ -10,11 +11,13 @@ import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 
 /**
- * 内存队列实现的线程安全Scheduler。<br>
+ * Basic Scheduler implementation.<br>
+ * Store urls to fetch in LinkedBlockingQueue and remove duplicate urls by HashMap.
+ *
  * @author code4crafter@gmail.com <br>
- * Date: 13-4-21
- * Time: 下午1:13
+ * @since 0.1.0
  */
+@ThreadSafe
 public class QueueScheduler implements Scheduler {
 
     private Logger logger = Logger.getLogger(getClass());
@@ -24,11 +27,11 @@ public class QueueScheduler implements Scheduler {
     private Set<String> urls = new HashSet<String>();
 
     @Override
-    public synchronized void push(Request request,Task task) {
-        if (logger.isDebugEnabled()){
-            logger.debug("push to queue "+request.getUrl());
+    public synchronized void push(Request request, Task task) {
+        if (logger.isDebugEnabled()) {
+            logger.debug("push to queue " + request.getUrl());
         }
-        if (urls.add(request.getUrl())){
+        if (urls.add(request.getUrl())) {
             queue.add(request);
         }
 
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/Scheduler.java b/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/Scheduler.java
index fc39b45..5b82dc7 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/Scheduler.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/Scheduler.java
@@ -4,23 +4,27 @@ import us.codecraft.webmagic.Request;
 import us.codecraft.webmagic.Task;
 
 /**
- * 包含url管理和调度的接口。包括url抓取队列，url去重等功能。<br>
- * Scheduler的接口包含一个Task参数，该参数是为单Scheduler多Task预留的(Spider就是一个Task)。<br>
+ * Scheduler is the part of url management.<br>
+ * You can implement interface Scheduler to do:
+ * manage urls to fetch
+ * remove duplicate urls
+ *
  * @author code4crafter@gmail.com <br>
- * Date: 13-4-21
- * Time: 下午1:12
+ * @since 0.1.0
  */
 public interface Scheduler {
 
     /**
-     * 加入一个待抓取的链接
-     * @param request 待抓取的链接
-     * @param task 定义的任务，以满足单Scheduler多Task的情况
+     * add a url to fetch
+     *
+     * @param request
+     * @param task
      */
-    public void push(Request request,Task task);
+    public void push(Request request, Task task);
 
     /**
      * 返回下一个要抓取的链接
+     *
      * @param task 定义的任务，以满足单Scheduler多Task的情况
      * @return 下一个要抓取的链接
      */
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/package.html b/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/package.html
index 7887dd5..e67edcc 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/package.html
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/scheduler/package.html
@@ -1,5 +1,5 @@
 <html>
 	<body>
-包含url管理和调度的接口Scheduler及它的几个实现类。
+Scheduler is the part of url management.
 	</body>
 </html>
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/AndSelector.java b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/AndSelector.java
index f13c6ed..135442d 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/AndSelector.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/AndSelector.java
@@ -4,6 +4,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
+ * All selectors will be arranged as a pipeline. <br>
+ * The next selector uses the result of the previous as source.
  * @author code4crafter@gmail.com <br>
  * @since 0.2.0
  */
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/CssSelector.java b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/CssSelector.java
index 90a9d1d..ab39186 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/CssSelector.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/CssSelector.java
@@ -10,10 +10,10 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
- * css风格的选择器。包装了Jsoup。<br>
+ * CSS selector. Based on Jsoup.
+ *
  * @author code4crafter@gmail.com <br>
- *         Date: 13-4-21
- *         Time: 上午9:39
+ * @since 0.1.0
  */
 public class CssSelector implements Selector {
 
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/OrSelector.java b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/OrSelector.java
index 4ece322..fd16dcb 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/OrSelector.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/OrSelector.java
@@ -4,6 +4,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
+ * All extractors will do extracting separately, <br>
+ * and the results of extractors will combined as the final result.
  * @author code4crafter@gmail.com <br>
  * @since 0.2.0
  */
diff --git a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/Selector.java b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/Selector.java
index 06756c4..3f4fe6b 100644
--- a/webmagic-core/src/main/java/us/codecraft/webmagic/selector/Selector.java
+++ b/webmagic-core/src/main/java/us/codecraft/webmagic/selector/Selector.java
@@ -4,13 +4,16 @@ import java.util.List;
 
 /**
  * Selector(extractor) for text.<br>
+ *
  * @author code4crafter@gmail.com <br>
+ * @since 0.1.0
  */
 public interface Selector {
 
     /**
      * Extract single result in text.<br>
      * If there are more than one result, only the first will be chosen.
+     *
      * @param text
      * @return result
      */
@@ -18,6 +21,7 @@ public interface Selector {
 
     /**
      * Extract all results in text.<br>
+     *
      * @param text
      * @return results
      */
diff --git a/zh_docs/us/codecraft/webmagic/Page-cmnt.xml b/zh_docs/us/codecraft/webmagic/Page-cmnt.xml
index 777f0b0..7ac44dc 100644
--- a/zh_docs/us/codecraft/webmagic/Page-cmnt.xml
+++ b/zh_docs/us/codecraft/webmagic/Page-cmnt.xml
@@ -24,7 +24,7 @@
      {@link #getHtml()}  get content of current page
      {@link #putField(String, Object)}  save extracted result
      {@link #getResultItems()} get extract results to be used in {@link us.codecraft.webmagic.pipeline.Pipeline}
-     {@link #addTargetRequests(java.util.List)} {@link #addTargetRequest(String)} add urls to crawl
+     {@link #addTargetRequests(java.util.List)} {@link #addTargetRequest(String)} add urls to fetch
 
  </pre>