Request From Error

Hi expert, I have a page which has the error below:
A potentially dangerous Request.Form value was detected from the client (emailString="...
Description: ASP.NET has detected data in the request that is potentially dangerous because it might include HTML markup or script. The data might represent an attempt to compromise the security of your application, such as a cross-site scripting attack. Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client (emailString=" In the page, I do have this line <@ Page validateRequest="false" %>

Pleas advise! Thank you!