Very aggressive advertisement.

I have no problem with ads or even videos that automatically start here on PF, but there is an ad at the top of the page that keeps stealing my page away when I am trying to read a thread.
It will keep snatching my page away, up or down until I click on it (Starbucks).
I can erase cookies later I suppose, but the process repeats itself again when I go to another page. It makes reading very difficult and frustrating.
I have also had to save and reload a page when things get very slow. I have lost the contents of my reply before and have had to start over. This doesn't seem to happen on other forums or websites I visit. Possibly it is a phpBB software issue? Something is loading the processor?
I wouldn't really call it a pop-up ad and I do have the pop-up blocker enabled.
I am on an iMac 10.12.5 with Safari 10.1.1.

That's something that I've never seen, even with a mobile device (and yes we know at the current time, mobile browsing of PF can be dodgy at times).

Have you tried a different browser to see what happens?

Unfortunately I'm not running a system that Safari supports, or I would give it a spin to see how it behaves for me.

Wally,
I have Safari on my ipad and I would imagine it's used the same as your iMac, (but I could be wrong). It will sometimes do that. I can't get rid of the ads. Usually restarting it helps.

As for losing your typed out work, sometimes you get logged out or "kicked out" and you can lose everything, so it's a good idea to copy what you have typed out just in case this should happen. I especially have to do this with PMs.

Have you tried using Google Chrome app? I haven't used it, but I know it can be used. I just personally prefer Safari.

I was glomming onto the advert issue, totally missed the losing a reply....

The only thing I've seen suggested for that, is to make sure you always have the 'log me in automatically' check box ticked. It seems to log a person out less often, that way, and I've very rarely lost a long reply or post, when I have that checked at login.

I also take back what I said about never seeing that with the advert- I had one browser, on one phone, running in a cached speed mode, that would do something like that- show the ad and not let me see the page, unless I clicked thru, and not always even then. But that was a hardware/browser combination that has never happened again for me. I'd look at seeing if your browser page caching is on, and see if that makes a difference. That, and try something like Chrome.

Thank you. It wasn't such a big deal, I just wanted to know if others were experiencing it. I did have regular Google and now have updated to the Chrome version.
I also installed AdBlock Ultimate. So far that has kept the hijacking away from the streaming ads.
I was avoiding an ad blocker as that had slowed down other (older) machines in the past.