The first question I always have when someone posts a question like yours is, Are you using a complete <!DOCTYPE> statement on your page? Unless you use a proper <!DOCTYPE>, browsers render pages in what's called Quirks Mode [en.wikipedia.org] where they all have their own differences. If you use a proper <!DOCTYPE>, all browsers render pages in "Standards Compliance Mode" in which they're all at least *trying* to render pages according to the W3C Standards. See the link above for details.
Beyond that, there are differences among the browsers as to which of the latest CSS methods that they support, but those are largely confined to enhanced visual effects. Layout issues are most commonly due to the <!DOCTYPE> issue. Good luck!