The .NET framework is throwing up an error because it detected
something in the entered text which looks like an malicious statement. The reason behind the error is as a security precaution. Developers
need to be aware that users might try to inject HTML (or even a script)
into a text box which may affect how the form is rendered.
The only workaround is to set the ValidateRequest attribute of the <%@Page directive to false
. Use <httpRuntime requestValidationMode="2.0" /> in your web.config if you are having ASP.NET 4.0 since it ignores ValidateRequest otherwise.