Computer response time needs to be under 1 second to allow visitors to maintain the flow of thought. And after 10 seconds, visitors completely lose focused attention. To keep loading time to under 1 second, assuming a 28.8 bit per second modem, requires that the entire page, including embedded graphics, be less than 3.6k bytes.
To keep loading time to less than 10 seconds requires that the page be less than 36k bytes.