Kan ikke kompile lokalt

Hejsa
Jeg har en webside som kører live men ikke lokalt. Det er ville være rart at få websiden til at køre lokalt, så jeg kan debugge. Jeg har forsøgt at kopiere dll-filer fra live serveren og det er til sidst lykkedes mig at kompilere websiden lokalt, men når jeg kører en side får jeg nedenstående fejl. Kan nogle guide mig videre?




FEJL:

Could not load file or assembly 'System.Web' or one of its dependencies. An attempt was made to load a program with an incorrect format.



[BadImageFormatException: Could not load file or assembly 'System.Web' or one of its dependencies. An attempt was made to load a program with an incorrect format.]
  System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +0
  System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +34
  System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +152
  System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +77
  System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +16
  System.Reflection.Assembly.Load(String assemblyString) +28
  System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +38

[ConfigurationErrorsException: Could not load file or assembly 'System.Web' or one of its dependencies. An attempt was made to load a program with an incorrect format.]
  System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +752
  System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +218
  System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +130
  System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +170
  System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +91
  System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +285
  System.Web.Compilation.BuildManager.ExecutePreAppStart() +153
  System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +521

[HttpException (0x80004005): Could not load file or assembly 'System.Web' or one of its dependencies. An attempt was made to load a program with an incorrect format.]
  System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +9950728
  System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +101