close page

I have some controls(textbox, label etc) in a Table of a page. I have an "Exit" button to close the page. 
the problem is if i just open the page and click the button, the page can be closed.
BUT if I input some things in textboxes and then click the exit button, the page won't be closed. Do not know why. the code is below:
<asp:Button ID="ButtonClose" runat="server" Text="Exit" ToolTip="Close Form" OnClientClick="window.open('', '_self', ''); self.close();return false;"/>
Need help. Thanks