how to make something similar to what kissmetrics does with their pop-ups?

See here: kissinsights.com on the demonstration?

How is this done? With and iframe?

EDIT: The pop up on the 开发者_运维百科side specially.

There are several different ways to do something like that. Javascript frameworks provide various animation mechanisms and utilities for fetching dynamic content. In this case, that site puts the "survey" in an <iframe> but whether you would do that or not completely depends on other aspects of your application.

So the short answer is that to do something like that, you write some software, possibly with the help of a framework chosen to suit your needs. If you run into specific issues in the course of such work, you should ask them here.