Window.open command only opens full window; height/width parameters do not seem to work

I'm using Visual Web Developer 2010 Express with SQL Server 2008 Express, VB.

The routine below opens a new window fine except that the height and width do not work.  The window opens full screen regardless of the height/width arguments.

        If FormView1.CurrentMode <> FormViewMode.ReadOnly Then
            Dim script As String = "window.open('Symbol_List.aspx', 'height=800,width=800', 'scrollbars=yes');"
            ScriptManager.RegisterStartupScript(Me, Me.GetType(), "popup", script, True)
        End If

Window.showModalDialog works but I need the window to remain open so the user can "refer" to it's contents while working in the parent window and window.showModalDialog doesn't allow that.

Does anybody know what the problem is and how to solve it?

Thanks!