Many people still use modems and other low-bandwidth links. Web page load times are often horrible because of the large graphics. Pick a few graphics of a few KB size and use them often instead of using lots of different graphics. Large graphics can often be small in KB if you are careful with the resolution and coloring. Small computers often use wireless modems, so the communication speed is not getting better as fast as one might think.
Large graphics take a long time to download because they are big.
This makes navigation hard and hurts usability of the web page. Review your web page on a small screen before you approve it. Give yourself at most two frames in order to avoid using all of the screen real estate. Review your web page on a small screen before you approve it.