Added AppNexus managed solution content (#1115)

* Added AppNexus managed solution content

* Edits per Jean's comments

prebid/managed.md

@@ -12,7 +12,7 @@ Several Prebid.org members will configure and host your Prebid implementations,
 
 <table class="cellpadding">
 <tr><td><a href="https://www.appnexus.com/en/publishers/header-bidding"><img src="/assets/images/partners/founders/appnexus.png" width="100"></a></td>
-<td>Offers a full set of managed solutions. Get started at <a href="https://www.appnexus.com/en/publishers/header-bidding">https://www.appnexus.com/en/publishers/header-bidding</a></td>
+<td>AppNexus, a Xandr company, offers a full managed Prebid solution including implementation and maintenance, as well as consulting support for publishers with their own tech resources. AppNexus works with users to enable client and/or server-side header bidding across web, AMP, and mobile app channels, and support display, video, and native ad formats. <a href="https://www.appnexus.com/contact">Contact AppNexus</a>for more information, and to get a quote! </td>
 </tr>
 <tr><td><a href="https://rubiconproject.com/headerbidding"><img src="/assets/images/partners/founders/rubicon.png" width="100"></a></td>
 <td>Demand Manager is a full service header bidding wrapper built on Prebid. Demand Manager’s technology and services allow streamlined implementation and wrapper management without custom development. Analytics and UI controls allow publishers and app developers to maximize Prebid’s performance. Demand Manager supports banner and video ads in web and mobile app environments. Get started at <a href="https://rubiconproject.com/headerbidding">https://rubiconproject.com/headerbidding</a> or reach out to your Account Manager for more.</td>