If your web system has no one more user system except the one from the forum,I think it is very easy to do the job.

But many people are using different CMSs to set up a web, which of course have their user systems. In order to make these CMSs cooperate with the forum, we must integrate them.

For the mylittle forum, its has a strict rule of activation on registeration,which makes it differ from many other CMSs. So if someone has just successfully registered in the other part of the web system, he can not login synchronously the forum until he has activate his account for the forum.

Before he activates his account for the forum, any time he clicks the link from other systems(which he has logged in) to visit the forum, the forum will automatically shift to the page in which says like this "You need activate your account, the mail has been send to your mail box:xxx@xxx.xxx,please go to ..."

After activation, the forum and other part of the web system would be a integrated system for the user, that's, he can login/logout synchronously the web from any part of the web system.