I just sent an email to engineeringcompgeek, but I’m following up here for everyone.
I logged on to the SD on a different computer than I usually use, and I am getting a pop up ad at the bottom of the page, both on the SD main page and on every board page load. This while logged in. It is my understanding that pop ups are not allowed here.
Fix it.
There is a bottom banner ad that is docked that is expected to run. We recently had problems with a particular ad that would cause a page redirect on android mobile devices, but this doesn’t sound like that and we believe that was isolated and removed. The bottom banner is intentional.
As Bone said, that’s a docked ad, not a pop-up, and as a guest you are supposed to receive ads like that. That’s what pays for your membership here. 
If ads like that bother you, feel free to install some sort of ad blocker. I’m not sure what device type and operating system you are running, but almost every device these days has an ad blocker of some sort available. We don’t prevent you from using the site just because you have an ad blocker installed.
In the last 2 days or so I began receiving another another pop-up ad on the main page. Not after I’ve logged in but while I’m logging in. This was not there for several weeks.
I’m getting something like that, a pop-up-and-under, as soon as I click in to sign in. Just on the page, no issue - just the usual banner. Start to log in and the pop happens and blocks the process.
Mac – Firefox
How is a “docked” ad different than a pop up?
Oh well, I guess I’ll have to avoid using other people’s computers.
A docked ad is an ad that is “docked” to a certain part of the page or screen. Typically, the docked ad remains in place even when you scroll up and down the page. Unlike a pop-up, with a docked ad, you can still generally use the page behind it, where a pop-up typically takes focus away from the page. There’s also a pop-under ad which typically spawns behind the current page and doesn’t take away focus. Different browsers handle docked ads, pop-ups, and pop-unders slightly differently. Some pop-unders get displayed in new tabs on other browsers, for example.
I personally find docked ads to be extremely annoying.