I can confirm. Regarding SPA in early days (before XMLHttpRequest): no one is doing that way, we can't find another developer thinking like that to help you, are you sure?.. (and browsers bugs)
I prototyped in Netscape Navigator.. had to fix it for IE.
Couldn't it be <a href="part.htm" target="dst"> just from the beginning ? - but what you got is AJAX, JS addictions and no caching.