iframe specific content?

On a page at my WordPress website I would like to embed/iframe a content.
For example this website:
Is it possible to put in just these forum posts on the page: http://ww.wp.xz.cn/support/forum/how-to-and-troubleshooting ?

For this site it seems to be a code that’s ” <table class=”widefat”> ” in the beginning, and I wonder if this class work to embed or iframe some kind of way into my blog.

The actual content I want to iframe/embed aren’t available on public yet, it requires a login for it. But it will be available in a few weeks for sure.
The current code for that is almost the same as this one, it’s ” <div class=”activity_stream”> “.

So therefor I wanna know if this is possible to do? If I can make some kind of embed or iframe that just takes a piece of the content of a website into my blog?
Are there any plugins for these?

I’ve searched for iframe plugins but haven’t got it to iframe specific contents.

Thanks in advance.