title: My website is unavailable after trying to upgrade from Umbraco 7.15.6 to Umbraco 8.1.0
body: <p>I tried to upgrade my website from 7.15.6 to 8.1.0</p>
  <p>I used FileZilla to copy /bin and /Umbraco to my host. Then, I edited the web.config as explained here: <a href="https://our.umbraco.com/documentation/Getting-Started/Setup/Upgrading/migrating-to-v8" rel="nofollow noreferrer">https://our.umbraco.com/documentation/Getting-Started/Setup/Upgrading/migrating-to-v8</a></p>
  <p>The installation process didn't start and my website is unavailable.</p>
  <p>When I tried to rollback to 7.15.6, I now get the following error: Parser Error Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.</p>
  <p>Parser Error Message: The type 'Umbraco.Web.UmbracoApplication' is ambiguous: it could come from assembly 'D:\home\site\wwwroot\bin\umbraco.DLL' or from assembly 'D:\home\site\wwwroot\bin\Umbraco.Web.DLL'. Please specify the assembly explicitly in the type name.</p>
  <p>Source Error:</p>
  <p>Line 1: &lt;%@ Application Inherits=&quot;Umbraco.Web.UmbracoApplication&quot; Language=&quot;C#&quot; %&gt; Line 2:</p>
  <p>Source File: /global.asax Line: 1</p>
  <p>Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4261.0</p>
  <p>I copied again /bin and /Umbraco to my host (of 7.15.6), as well as the config and App_Plugins folders</p>
  <p>How can I bring my website back???</p>
  <p>Thakns.</p>