center align

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1689307 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/site/xdoc/index.xml b/src/site/xdoc/index.xml
index 28afdfc..f1828a8 100644
--- a/src/site/xdoc/index.xml
+++ b/src/site/xdoc/index.xml
@@ -33,7 +33,7 @@
     </p>
     
 <div align="right">
-<pre style="width: 625px;">
+<pre style="width: 625px; text-align:center;">
 +---------------------+-------------------------+----------------------------+
 |         BSP         |           Graph         |        Deep learning       |
 |      (pure BSP)     |     (Google's Pregel)   |    (Google's DistBelief)   |