I think you have problem for getting server side error when enter html code in textbox. For the security reason asp.net does not allow this. But you can enable it by making <%@ Page validateRequest="false" %>

Mohan

Ajax tool kit provides the nice calender extender controls to solve your problem. You can see the sample example on http://www.asp.net/ajax/ajaxcontroltoolkit/Samples/Calendar/Calendar.aspx[^]

Mohan