Rendering Problem in Internet Information Services 7:

When using the SQL Server Reporting Services (SSRS) Report Viewer control, an issue can occur when published through Visual Studio 2008 and used under Internet Information Services (IIS) 7. This Issue occurs because Visual Studio 2008 compiles the Report Viewer web project for use within IIS 6, and sets the Web.Config file settings to reflect this. In order for the report viewer control to work under IIS 7 the Http Handler setting must be added to the Web.Config file.

Find the system.web and httpHandlers tags and insert the add tag as illustrated below: