IF you are facing issues , adding a question to a sharepoint survey , adding a new column to a list or document library and you are getting this error in the ULS logs
Getting Error Message for Exception System.Web.HttpRequestValidationException (0x80004005): A potentially dangerous Request.Form value was detected from the client (FieldXML="<Field Type="Choice"...").
1- Go to the web.config of your application
2- Add a new entry under <system.web>
3- Also Find the pages tag and set validateRequest=False