hosting website Access to the path 'D:\inetpub\vhosts\siwebsoft.com\httpdocs\App_Data\work\user1\09-26-2012\' is denied.

Hi folks,
I've uploaded my webapplication to ftp. When I run this application from local host, it works fine..
But the same on the website gives me this error:
System.UnauthorizedAccessException: Access to the path 'D:\inetpub\vhosts\siwebsoft.com\httpdocs\App_Data\work\user1\09-26-2012\' is denied.
 Line 606: string userPath = GetUserFolder();
 Line 607:     string fullPath = GetUserFolderForToday(userPath);
Line 608: if (!Directory.Exists(fullPath))
Line 609: {
Line 610: Directory.CreateDirectory(fullPath);
Line 611: }
My code wri ...