Compatibility of website with browser's

Hi all,
I am developing a website and currently the issue is of browser compatibility.The website is running correctly in Internet Ex7&6,but the positioning of text changes in the other briwser's namely firefox,chrome and IE8.i am trying to use conditional statements in my source but the results are not fruitful.What is the correct way to use the conditional statements in the source.Please help me out.It's urgent.
Thanks in advance
Vineet