first I have to say your products are great and while

Hi, first I have to say your products are great and while there's a learning curve it offers more than most of the other -all in one solutions marketed. Believe me, I tried alot and spent alot to try..
Im having issues with responsiveness. I have a div containing an iframe on several of my pages. If I just put the iframe, for the most part it's responsive. With the div however, it remains the same size. If I modify the div size say in mobile, the change affects the tablet and desktop views as well.
Please advise. Thanks, John.