htmlfile: Could not complete the operation due to error 800a025e

Question

My Code is as follows: function SetToEnd(txtMessage)

        {                    
            if (txtMessage.createTextRange)
            {
                var fieldRange = txtMessage.createTextRange();
                fieldRange.moveStart('character', txtMessage.value.length);
                fieldRange.collapse();
                fieldRange.select();
            }
        }



 <asp:TextBox Id="txtMessage" onkeyup="ReplaceChars()" onfocus="SetToEnd(this)" runat="server" MaxLength="100" Width="500px" />

The problem that the error "htmlfile: Could not complete the operation due to error 800a025e" is being thrown continously