That’s not iframes, it is something to do with your
parts and your CSS.
1) Your CSS is styling the CODE tag so that it is in a scrollable area, which is handy for code on forums like this.
2) I don’t actually know why you have CODE tags anyway, and suspect you have done something very silly when copying example code from here. At a guess, each of your template chunks contains only <CODE> html, and not the contents of the example code.
EDIT: Ah, you’ve posted the ditto code now. That’s fine, so clearly it is the template that is at fault. Can you post the template?