"Errors were found when compiling the workflow.The workflow files were saved but cannot be run."

When you create workflow using sharepoint designer tool and you get the following error:-

 "Errors were found when compiling the workflow.The workflow files were saved but cannot be run." and if you click on details button you get message "Unexpected error on server associating the workflow".

The problem with your web.config file. If you install some third party workflow tool(e.g Nintext,Sogeti,EdinKapic) and unistall it, referrence dll not removed from your web.config file. 

To remove error use following steps:-

1. Open your web.config file in Visual studio.
2. Go to "<System.Workflow.ComponentModel.WorkflowCompiler>"
3. The third party workflow tool reference available here. e.g. Sogeti.Workflow tool
4. <authorizedType Assembly="Sogeti.Workflow.Activities,Version=1.0.0.0, Culture=neutral, PublicKeyToken=1cdaea2144644b9c" Namespace="Sogeti.Workflow" TypeName="*" Authorized="True" />
5. Comment the third party tool reference, you uninstall previously.
6. Save web.config file and reset server.
7. Now your workflow run normally.