But I don't think using iframes is good for SEO purpose as it makes website heavy and slow.
I do wish they used OBJECT instead, but again OBJECT was originally supposed to be to replace APPLET and IFRAME in 4 Strict, it's why EMBED wasn't accepted into the specification, and we were allegedly supposed to by the next HTML version stop using IMG as well in favor of object.
Which of course is why the train wreck of pointless bull known as HTML 5 backpedalled on that, accepted EMBED into the spec for no good reason, and added the pointlessly idiotically redundant AUDIO and VIDEO tags.
That said, the page in question just looks like a normal hover state / dropdown. You do know how to use :hover in your CSS, right? If I was implementing that I'd just set the inner "window" type div to position:absolute, and the outer div to overflow:hidden; When you add :hover on the parent just set it to overflow:visible and poof, that dropdown shows up.
... and please, don't copy their gibberish use of a H4.