Erro ao gravar registro no banco

O que é isso pessoal ? Quando tento gravar dá esse erro....agradeço a ajuda ! A potentially dangerous Request.Form value was detected from the client (tb_Descri="...XCOR PLUS <CONCRETO>"). 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 (tb_Descri="...XCOR PLUS <CONCRETO>").