start talking about polymer.dart

src/site/articles/web-ui/index.markdown

Index: src/site/articles/web-ui/index.markdown
diff --git a/src/site/articles/web-ui/index.markdown b/src/site/articles/web-ui/index.markdown
index 767525b8ea205d5d97ae6914d88acc5f593c55ce..c289b01fe1b5d2d1449c1a7bc154ac4579b0aadf 100644
--- a/src/site/articles/web-ui/index.markdown
+++ b/src/site/articles/web-ui/index.markdown
@@ -44,8 +44,25 @@ that will contain the running version of the code sample.
 {% iframeprefix example/ %}
 {% endcodesampleSetup %}
 
+<div class="hero-unit">
+      <h1> Introducing Polymer.dart </h1>
+      <p markdown="1">
+        [Polymer.dart](/polymer-dart/), the next evolution of Web UI, has
+        better debugging,
+        faster development, and closer spec alignment.
+      </p>
+</div>
+
 # {{ page.title }}
 
+<aside class="alert alert-danger" markdown="1">
+<strong>Web UI is now Polymer.dart.</strong>
+Web UI has evolved to
+[Polymer.dart](/polymer-dart/), which provides many fixes and improvements.
+We encourage Web UI users to upgrade to Polymer.dart.
+The information on this page apply only to Web UI, which is now deprecated.
+</aside>
+
 _Written by Sigmund Cherem<br />
 October 2012 (Updated February 2013)_