Due to the way that Marketo landing pages are built (absolute positioning, non-standard DOM rendering), there is no "one size fits all" piece of code to make pages differently based on device. That being said, Marketo's system should support al modern browsers with its default coding.
Hey Michelle- Without seeing the desktop version of your site, the thing that sticks out the most immeidately is the "* are required" running into First Name. What I suspect is that Webkit uses a slightly different sizing for line-spacing than a PC does. This happens to me all the time with Marketo pages. My Mac & my PC render the page & fonts differently, so I have to be aware not to produce pages which are too tightly fitted. This is the basic problem with absolutely positioned documents, they have no awareness of their neighbors so they don't flow properly.