The attached Zip file is really an epub. To use it as such, rename it with an epub extension. The forum software won't let me upload it as an epub, even though it is really a zip file. You can either use the epub as is, or just unzip it and view the HTML file in your browser.
The content is totally bogus. I just made it up for this test. I used a <span> tag to mark the beginning few words of each page. Since a physical page is likely to fall mid-sentence, you can't use a block-level tag like <div>. Well, you could, but that would also break a sentence in the ebook, which is not what you want.
As for using a background color on the words that start a physical page, that isn't exactly ideal for ebook reading, either. I just did it to make it easier to see exactly where my imaginary page breaks were. Without some visual clue, you'd have to carefully scan the first few lines to match up the words, after jumping via the "table of pages" that I made at the end.
This is far from an ideal method, but it was the first thing that I tried. Perhaps someone has a better suggestion? How to delimit the page breaks for those who need them, while not being in-your-face for the average ebook reader? In a web browser, some javascript could make this a lot easier. However, I don't know of any ebook readers that do javascript (not counting PDAs).