+* Rails 4.0 requires routes using `match` must specify the request method. For example:
+# Rails 3.x
+ match "/" => "root#index"
+ match "/" => "root#index", via::get
+ get "/" => "root#index"
* Rails 4.0 has removed ActionDispatch::BestStandardsSupport middleware, !DOCTYPE html already triggers standards mode per http://msdn.microsoft.com/en-us/library/jj676915(v=vs.85).aspx and ChromeFrame header has been moved to `config.action_dispatch.default_headers`
Remember you must also remove any references to the middleware from your application code, for example: