**EDIT** This has somehow been resolved. I'm not exactly sure how I fixed it, but deleting the sub folder, recreating it, and re-adding it as a web app seemed to work. Sorry for the trouble. I am getting an "HTTP Error 500.19 - Internal Server Error" when I try to hit this url: a sub-folder of my main site (www.mainsite.com/subfolder). When I hit the main URL: www.mainsite.com I get the error below, but If I remove the JustDev folder and remove it as a web application, the main URL works again. ----------------------------------------------- Configuration Error Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Could not load file or assembly 'System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. Source Error: Line 65: <add assembly="System.Web.Abstractions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Line 66: <add assembly="System.Web.Routing, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Line 67: <add assembly="System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> Line 68: <add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> Line 69: <add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> Source File: E:\web\sitename\[....]\web.config Line: 67 Assembly Load Trace: The following information can be helpful to determine why the assembly 'System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded. ------------------------------------------------------------- I have that assembly set to copy-local and can see it in the bin folder where it should be. All of this was working without issue, but I recently renamed the project and root namespace, which I assume is causing the issue. The only thing that was changed in the web.config was the Membership provider type: from projectName.Providername to projectName_dev.ProviderName Is there anything in particular that I need to do to make this work again? My site is currently unusable because of this; please help ASAP. Thanks for your time!