IE6 has a particular set of display issues that need to be addressed separately and one of the methods you could use is to have a style sheet that is specific to IE6. In other words, your normal style sheet is declared first then you declare a style sheet just for IE6 that will correct any css rules or styles that do not render as required.
You will need to determine which of your styles looks incorrect and then place a correction for them in the IE6 style sheet. Go look up things like the box model hack and anything else that might be causing a problem.
Here is one way to declare an IE6 only style sheet:
<!--[if IE 6]>
<link rel="stylesheet" href="Styles/IE6.css" type="text/css" media="screen" />
Of course you can also use this method if you had specific styles for IE7, etc.