Just for starters, do yourself a favor and always use a <!DOCTYPE> that will put browsers in Standards Compliance mode. That will minimize the differences in how browsers render your pages. If you start designing for Quirks mode for one browser version/family, you'll almost always have problems and your code will be much more difficult to maintain.
That said, there's little in your code fragment that I would expect to be a significant issue. You might set a specific margin on the INPUT tag if the positioning varies, I suppose. What seems to be the exact problem?