Best way would be to test your site in various browsers and work on the elements that are distorted/misplaced in specific browser. Then test again on all browsers to see if the fix affects other browsers. Repeat the steps until you are satisfied with the results.
One thing you should remember is that sometimes it's not your site that is messed up but it's the browser that is either not upto standards (hello IE) or there is a bug in the browser.
IE is a few pixels off from FF, so if you're really spacing things tightly, the page will either have small gaps or be stacked on top of itself in some places. This causes a major headache when designing.