Help me pick a doctype, help Options

[Maccabee]

what doctype do I need to use?

Here is the code:

CODE

<html>
<head>

<title>my title</title>
<link href="stylesheet.css" rel="stylesheet" type="text/css" />
<meta name="description" content="description" />
<meta name="keywords" content="keywords" />

</head>

<body>








<div align="center">

<div id="pagewidth">
<br>


<div id="header"></div></center>

<div class="floatcontainer">


<div id="navigation" >

the nav

</div>







<div id="content" >
<h2>Welcome</h2>Hey

</div>
</div>



<div id="footer" >
<hr style="height: 5px; border-style: none; background-color: black; color: black; width:80%;">


<br>

<u>copy</u>
<br><br></div>
</div>

</div>
<br>
</body>
</html>

Do you need to see the css too?

And how come any time I put in any doctype it messess up my floating divs in ie6?