No. Not all all.
On a jsp page, there is field, next to it is a search button. When it is pressed, the div stands out (feeling like a popup), but it is not. It is just raised by z-index. It has several search fields on it.
No the screen looks like this:
DIV (so called popup) on top
iframe bahaves like a screen with 50% opacity to allow the user still look through to see the content of the main body
the bottom (z-index=0) is the main body content.
--I mean for this purpose, is the iframe necessary?