diff --git a/docs/faq.rst b/docs/faq.rst
index 66cae3d16..c0b76b21f 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -203,3 +203,13 @@ To dump into a XML file::
     scrapy crawl myspider --set FEED_URI=items.xml --set FEED_FORMAT=xml
 
 For more information see :ref:`topics-feed-exports`
+
+What's this huge cryptic ``__VIEWSTATE`` parameter used in some forms?
+----------------------------------------------------------------------
+
+The ``__VIEWSTATE`` parameter is used in sites built with ASP.NET/VB.NET. For
+more info on how it works see `this page`_. Also, here's an `example spider`_
+which scrapes one of these sites.
+
+.. _this page: http://search.cpan.org/~ecarroll/HTML-TreeBuilderX-ASP_NET-0.09/lib/HTML/TreeBuilderX/ASP_NET.pm
+.. _example spider: http://github.com/AmbientLighter/rpn-fas/blob/master/fas/spiders/rnp.py