On a few pages, their source code includes:
<meta name="Generator" content="Drupal 7 (http://drupal.org)" />
and
<span>Powered by <a href="http://drupal.org">Drupal</a></span> </div>
,which leads be to believe its Drupal.Net since standard Drupal is PHP not .NET. I thought maybe they used to be PHP and switched, but checking their internet archive all the way back to 2003 they have always been using asp(x) pages. If you look at the first screenshot of Drupal.NET, it looks almost identical to the angieslist template.
Also I found this snippet on their contact page:
<a href="http://rightnow.com/cx.html" target="_blank" title="Powered By RightNow Technologies">
<span class="rn_ScreenReaderOnly">Powered By RightNow Technologies</span></a>
Edit
This is very interesting... if you do a header check on a normal page you get:
HTTP/1.0 200 OK =>
Cache-Control => private
Content-Type => text/html; charset=utf-8
Server => Microsoft-IIS/7.5
X-AspNet-Version => 4.0.30319
X-Powered-By => ASP.NET
Content-Length => 25475
Date => Thu, 04 Oct 2012 22:47:43 GMT
Connection => close
Set-Cookie => ALREG-1=exp=10/4/2012 6:47:44 PM&memType=2; domain=.angieslist.com; expires=Sat, 04-Oct-2014 22:47:44 GMT; path=/
I found if the url has invalid without a trailing slash, like /404test it gives a 301 to the trailing slash version:
HTTP/1.0 301 Moved Permanently =>
Server => nginx
Content-Type => text/html
X-Drupal-Cache => MISS
Expires => Sun, 19 Nov 1978 05:00:00 GMT
Cache-Control => no-cache, must-revalidate, post-check=0, pre-check=0
ETag => "1349391009"
Content-Language => en
Last-Modified => Thu, 04 Oct 2012 22:50:09 GMT
Location => http://www.angieslist.com/404test/
X-AH-Environment => prod
Vary => Accept-Encoding
Content-Encoding => gzip
Content-Length => 20
X-Varnish => 1990526627
Date => Thu, 04 Oct 2012 22:50:09 GMT
Connection => close
Then trailing slash version throws the 404:
HTTP/1.0 404 Not Found =>
Server => nginx
Content-Type => text/html; charset=utf-8
X-Drupal-Cache => MISS
Content-Language => en
ETag => "1349391152-1"
X-Generator => Drupal 7 (http://drupal.org)
Cache-Control => public, max-age=86400
Expires => Sun, 19 Nov 1978 05:00:00 GMT
Last-Modified => Thu, 04 Oct 2012 22:52:32 GMT
X-AH-Environment => prod
X-Varnish => 1990530957
Vary => Cookie
Date => Thu, 04 Oct 2012 22:52:32 GMT
Content-Length => 19329
Connection => close
and if you send a HTTP 1.0 request without HOST, you get:
HTTP/1.0 400 Bad Request =>
Server => AkamaiGHost
Mime-Version => 1.0
Content-Type => text/html
Content-Length => 193
Expires => Thu, 04 Oct 2012 22:55:16 GMT
Date => Thu, 04 Oct 2012 22:55:16 GMT
Connection => close
So not really sure what to make of that, Very strange...
.aspx
extensions you can tell that they use Microsoft ASP.Net