doc: fix root.html styles

R=r
CC=golang-dev
https://golang.org/cl/7442045
diff --git a/doc/root.html b/doc/root.html
index cc2bfd1..34915c0 100644
--- a/doc/root.html
+++ b/doc/root.html
@@ -53,11 +53,11 @@
 <div id="gopher"></div>
 
 <a href="/doc/install" id="start">
-<div class="big">Download Go</div>
-<div class="desc">
+<span class="big">Download Go</span>
+<span class="desc">
 Binary distributions available for<br>
 Linux, Mac OS X, Windows, and more.
-</div>
+</span>
 </a>
 
 </div>