A lot of early web apps heavily abused this pattern - I worked on a web framework that used iframes to manage widget state, and of course at that time everyone

A lot of early web apps heavily abused this pattern - I worked on a web framework that used iframes to manage widget state, and of course at that time everyone had to support IE5 and 6. But those browsers by default had this charming noise (an audible click) every time a page loaded or iframe loaded. When you would click a widget button you’d here this curious storm of clicks as the iframes all reloaded. That culminated in a super awesome bug called “The Click of Death” where sometimes on IE6 you’d click an interface element, hear a huge train of clicks, and then ominously, it would fall silent and IE would freeze (hard lockup, no browser interaction possible). Turns out we were deadlocking on CSS and JS loads in those iframes - IE6 only allowed two simultaneous connections, and if you got out of order you couldn’t load an iframe because the connections were waiting to clear the CSS item the JS needed to load.