Dial-Up Modem Usage
Every now and then in some discussion group, an outspoken individual will proclaim that dial-up is dead, almost "everyone" has high speed broadband access, and that web designers don't have to worry about dial-up anymore. Often these individuals are college students with little world experience, but that's beside the point. What really matters is they couldn't be more wrong. I finally came across some recent numbers:

There are approximately 70 million people with internet access in the US.
Number who access with:
Internet TV: 1 M
DSL: 3 M
Cable modem: 5 M
Dial-up modem: 61 M
[source: Information Technology Association of America]

Obviously each site needs to determine it's own user base and if dial-up users are a significant (or important enough) fraction to warrant concern. However the implication is clear: if you want your site to be usable for the greatest possible number of visitors, the design must be optimized for fast loading on a dial-up connection. And that doesn't mean 56Kbps. A huge majority of phone lines and switches aren't clean enough to support even that speed. The sites must be optimized for 28.8Kbps and even at that, a significant number of dial-up users with 56K modems will actually connect at 14.4Kbps.