Most likely cause is incorrect NTFS permissions on the root folder, but without corresponding windows event log it's just a guess.

i did some changes and now i am getting this error does any body know how to remove this

Server Error in '/dnn3' Application.
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Failed to access IIS metabase.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.Hosting.HostingEnvironmentException: Failed to access IIS metabase.

The process account used to run ASP.NET must have read access to the IIS metabase (e.g. IIS://servername/W3SVC). For information on modifying metabase permissions, please see http://support.microsoft.com/?kbid=267904.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace:


[HostingEnvironmentException: Failed to access IIS metabase.]
   System.Web.Configuration.MetabaseServerConfig.MapPathCaching(String siteID, VirtualPath path) +3591442
   System.Web.Configuration.MetabaseServerConfig.System.Web.Configuration.IConfigMapPath2.MapPath(String siteID, VirtualPath vpath) +9
   System.Web.Hosting.HostingEnvironment.MapPathActual(VirtualPath virtualPath, Boolean permitNull) +169
   System.Web.CachedPathData.GetConfigPathData(String configPath) +389
   System.Web.CachedPathData.GetConfigPathData(String configPath) +243
   System.Web.CachedPathData.GetApplicationPathData() +68
   System.Web.CachedPathData.GetVirtualPathData(VirtualPath virtualPath, Boolean permitPathsOutsideApp) +3536567
   System.Web.Configuration.RuntimeConfig.GetLKGRuntimeConfig(VirtualPath path) +189

 


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Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433