The only way to prevent this error from appearing is to turn off Request Validation or remove the tags from your textboxes when submitting the form. If you want to keep these values, you can change you RadTextBox controls into RadEditor controls, if that is the kind of input you want to accept.
I hope that helps.
answered on 10 Dec 2012, 09:38 AM
One option to avoid this behavior is to attach the OnKeyPress event of RadTextBox and cancel the event if invalid character is pressed.
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