Description: Request Validation has detected a potentially dangerous client input value, and processing of the request 
has been aborted. This value may indicate an attempt to compromise the security of your application, such as a cross-site 
scripting attack. You can disable request validation by setting validateRequest=false in the Page directive or in the  
configuration section. However, it is strongly recommended that your application explicitly check all inputs in this case.


Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was 
detected from the client 
hello ...").

This could easily be fixed


just add validateRequest=false in the top most line @ Page