Tom and Rob addressed the problem of paging backward pretty well. Sometimes the "Earlier" button doesn't show, and I never have been able to figure out the pattern and fix it.

Bookmarking a post can be a little unclear because of the way the page is laid out. The top and left sides represent a Web page (the current board), and the post in the center is another page embedded inside that one. This means that the message has a different address than the outer page, and you have to be sure you're bookmarking the right page.

The address in the box at the top of the browser is for the outer page, and to make it even more confusing, that's the first outer page (board) where you started, and if you change boards, the address stays the same. This has often led people to copy the address in the box thinking it was the message, but it's not.

The "authoritative" source for the message address (URL) is the link you see at the bottom left below the message, "Message URL" (which I had to add because so many people ran into the problem you've encountered--you're not alone by any means).

In FireFox, you can hover the mouse over the link and right-click to display a little menu. Pick "Bookmark This Link..." to make a bookmark from it. Use "Copy Link Location" if you want to copy-n-paste the address into a post.

In IE7, hover the mouse over the link, right-click, and select "Add to Favorites...". IE isn't as clear as FireFox, so you have to be sure you really are hovering over the link. Use "Copy Shortcut" to copy-n-paste the address.

Bit by bit, byte by byte, we're gonna make a Geek (or is it Geekette?) out of ya yet.