Sometimes I leave the forum and do not remember where I have been exactly. Is there a function to mark the exact place ?

use the bookmark function of your browser.

The forum is designed to track topics and posts. If you've made neither it won't remember. You can find your own posts in your profile. If you want to "bookmark" certain topics, you can use the Watch Topic button at the top of each one. I do this to "remember" certain topics that I find I may need to reference often, for the help of forum users or personal reasons.

Odd - one innocuous (and nonsense) post "Vista Business x86" and never returned.