Tiny MCE ASP.NET and RequiredFieldValidator

To make validator work wity Tiny MCE, you need to update textarea before the validation starts.
To update it, call tinyMCE.triggerSave(false, true) method in your button event.

<asp:Button runat="server" ID="BtnCommit" <br />OnClick="BtnCommit_Click" CssClass="buttonclass" <br />Text="Submit" style="float:right;"<br /> OnClientClick="tinyMCE.triggerSave(false,true);"/>