Code:
<script language="javascript">
var myVar = "Hello World";
window.open("page.php?myVar=" + myVar);
</script>
You can pass them though Get, via the query string, or you can do something a little more complex and pass them though POST
Code:
<form id="article">
<input type="hidden" value="" id="action"/>
</form>
<script language="javascript">
var action = document.getElementById("action");
action.value = "previewarticle";
var frm = document.getElementById("article");
frm.target = "_NEW";
frm.action = "yourpage.php";
frm.submit();
</script>
There might be some better ways of doing this so if your still suck your best bet would be to ask the lovely people in XML, HTML, Javascript, Web and CGI