Hi Dale,
This isn't Classic ASP. You can't just response.write stuff in button click events and expect things to work right.
The right way to do it is to just use a link.
<asp:HyperLink ID="lnkDetails" runat="server" />
In code you can make the link open a new window by setting it up like this:
lnkDetails.Text = "Your link text";
lnkDetails.NavigateUrl = "yourdetailspageurl.aspx";
lnkDetails.Attributes.Add("onclick", "window.open(this.href,'_blank');return false;");
Note that using the onclick and javascript to open the page in a new window is preferrable to using the target attribute because target is not a valid attribute in xhtml
Hope it helps,
Joe