This just happened again, so I thought I’d mention it:
When I’m reading here, I go to a forum, browse down the page, click into a thread I want to read, then, if I don’t post, click the back arrow to go back to the forum page.
What has happened at least a half dozen times over the last week or so is that instead of going to the previous page, I go to the page before that, which might be elsewhere in the SDMB site or might be wherever I was elsewhere on the net prior to coming into the Dope. (My bookmark takes me to the MPSIMS forum page, so if it happens in the first thread I read in MPSIMS, two clicks back would be offsite.)
If I check the dropdown, there’s no sign of my having been on the intervening forum page.
This might sound stupid – and if it does to you I apologize – but what I do is essentially a two-tab method. I call up a forum page and then click into a thread using the “Open thread in new tab” function. Then I have an independent tab window to work with without disturbing the forum page. I read the thread, respond as needed, or just close the tab. Then I can return to the forum page whenever I need to without waiting for the page to be re-rendered again. I can also change to a new forum page as needed by simply dropping to the menu below.
This seems to me to be the most efficient way to read the board; it’s fast and doesn’t take up a lot of resources. I thought that’s why they made tabbed browsing in the first place. 
I’m an old-fashioned girl. I’ve usually got four or five tabs open for different sites, but navigate around each site in a single tab – otherwise I’ve just got too fucking much open at once.
Anyway, since I do use the forward and back arrows, I thought I’d mention this – this is the only site where this happens.
It’s not a huge problem for me, just some minor, recurring, weirdness.
Which browser are you using?