//验证FCKeditor是否为空

function FckCustomValidate(source, arguments) {

    var fckFrame = document.getElementById(source.controltovalidate + "___Frame").contentWindow;

    var value = fckFrame.FCK.GetHTML(fckFrame.FCKConfig.FormatOutput);

    if (value == "") {

        arguments.IsValid = false;

    }

    else {

        arguments.IsValid = true;

    }

}

<FCKeditorV2:FCKeditor ID="fckContent" runat="server" Width="100%" Height="400px">

        </FCKeditorV2:FCKeditor><asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="必填" ControlToValidate="fckContent" ClientValidationFunction="FckCustomValidate"></asp:CustomValidator>