There's information out there about developing for the iPhone... like Apple's site for example. Though I'm too lazy to locate it. There's also an app that supposedly emulates an iPhone called
iPhoney. I think I used a previous version, but it had some issues in terms of scaling. Basically the page will show up like it does in Safari, or scaled down if it's too large (there's also something you can put in the header to give yourself more control over the scaling). Make sure you don't have tiny links or anything that's hard to click.