what does this mean?

[davio33]

When i go into "who's online" and look to see users locations, sometimes I will see locations like this: "
website.com/forums/threads/threads/threads/6545-actual-thread-name"

or this

"website.com/forums/threads/6545-actual-thread-name"

when i click these i get a page not found.

But if i go to "website.com/threads/6545-actual-thread-name" the thread does actually exist.

Im just wondering whats happening here, why am i seeing people looking at urls witch dont exist, why is /forums/threads/threads/threads/ or /forums/threads/ showing up

thanks. hope someone can help. not sure if visitors are getting bad pages or not