Well, for starters almost all PocketPCs have screens of 240 pixels wide by 320 pixels high. I'm not sure about smart phones but I suspect that many of them will be smaller than this. Then you have the newer PDAs that have higher res screens and it all gets a bit complicated.
You could just design your page to fit in a 240 x 320 window and it would then work fine with most current PocketPCs but that's not really the right solution. Here is what I'd recommend:
- Don't have too much text otherwise users will have to scroll a lot
- If you must use images then use them sparingly and keep them small
- Try not to use fixed layouts (tables with fixed sizes, fixed font sizes and so on)
- Don't use anything like Flash as the user may not be able to view it at all
- Big files like animated GIFs (many users will likely be viewing your site over slower wi-fi connections)
- Let the user's browser handle the layout
- Don't forget that not everyone uses Internet Explorer, so don't target your site at a particular browser.
Hope that's helpful!
Nelviticus