It is impossible to totally control how others will view/render your page (browser differences, user preferrences, hardware differences).
Therefore, advice I've always found valuable is to design your site so that it doesn't rely on specific formating. Sure there are some sacrafices with aestetics and it does require a bit more time and planning, but you run a lower risk of people looking at a site (a reflection on your skills) and wondering what in the world they're seeing.
Besides, people MAY have very valid reasons for surfing with large fonts or other setting quirks (i.e. seeing disabilities). Content is king so I'd make sure your content comes across without formating specifics.