Brion Vibber wrote in part:
Netscape 4.x and Internet Explorer (at least the 5.5 I have) are so overzealous about these that they force a reload even when using the forward and back buttons. Mozilla (and presumably Netscape 6 and 7) are saner about this, and consider the page still open -- forward and back aren't page load events, they're just showing you things you've already opened again.
Netscape 6 has the same behavior as Netscape 4 and IE 5 (all for Unix). This has annoyed me in other situations as well.
-- Toby