We've got pop-ups and pop-unders, so these must be slide-outs.
I'm not sure which page i've been going to that creates them, or i'd try it for experimental research, unfortunatly every time they pop up, er slide out, on their own, it's just unnerving and triggers an instant "delete it!" reaction.
They either start out off the edge of your screen, on the bottom of the right side, or right of the bottom edge in the cases i've see so far, or are minimized along that edge. They then slide out onto your screen, or are expanded into it in a smooth motion. They almost seem to be crawling onto your screem from under the edge of the monitor. It's really kind of disturbing.
They _do_ get more noticed by me than pop-ups or pop-unders, they're kind of feaky and disturbing. Nothing should be moving on my screen unless i told it to or told a program to run that does it. Ads being able to locomote about on their own is creepy. Of course rather than getting me to actually look at them, their behavior causes me to go "Ack! Delete it!" as soon as i notice them.
The only one that's actually managed to register on my consciousness at all was advertising something about Spiderman.
I just saw another one pop up, so this time i resisted the desire to KILL KILL KILL! KILL IT NOW!!!! *catches his breath*
It was an add for "Celltena," which is "as seen on tv, for only $19.95" =P (Yes, i'm repeating their information, rather than viewing it as further advertising from them, view it as an advisement to run screaming from their products if you ever see them =)
It also had a little countdown timer, "closing in 25" (or was it 30) which then proceded to count down. At the end, it slowly slid back down beneath the bottom edge of my screen, like some ancient evil creature returning to the depths from whence it came. *shiver*