aspx page
within header
<script type="text/javascript">
function NewWindow()
{
top.window.open("http://www.google.com",'800x300','toolbar=no,scrollbars=yes,resizable=yes,status=no,location=no,menubar=no,directories=no,width=800,height=300');
}
</script>
and within form
<asp:Button ID="Button1" runat="server" Text="New Window" OnClientClick="NewWindow()" />
<input type="button" value="New Window" onclick="NewWindow()" />
<a href="javascript:return fasle" onclick="NewWindow()"> New Window</a>