I suspect this is mainly a post for Mark, but anyone is welcome to aid my confusion.
I am an avid reader of the forums here, and I like to read them all: even the subjects in some (such as the medium format forum) which will almost certainly never affect me directly can be of interest. I find the option to "show posts since your last visit" to be invaluable. However, I find that I am quite often missing posts, and indeed whole topics, because they don't appear in the list after I click this option.
Is this due to bugs in the forum software? Or have I perhaps not understood what's meant by a "visit"? Is my last "visit" when I arrived, or when I left? How is when I leave defined? Must I log out (which I don't do), or merely close the browser window?
I'm using Safari on Lion, and reading at various times from my laptop, my desktop and my iPad.