If you need to create really complicated content with a lot of loading data, a lot of pages, animations, pictures and so on, this is an important issue.
I made every page as a separated document. When i knew how many pages i needed and what was in there, i created the container document which includes navigations, too.
I sent independent pages in container folder. Whole bunch are now in recources folder of my container file, which is light weight.
Only thing you need to care is that link in iframe refers in right document.
Text is in Finnish but you find the idea easily.