I am NOT talking about zooming the page, but rather the way MobileSafari on iOS automatically bumps up some font sizes sometimes.
When, exactly, is this done? Can it be prevented or discouraged?
body {
-webkit-text-size-adjust: 100%;
}
Just make sure all your text is at a legible size in the first place. The iPhone and iPod touch have a rather small screen, so keep that in mind too.