If you're writing XTHML 1.0 then you'll not be able to use the target attribute to open links in a new window AND have the page validate as XHTML. You can get around this with the use of JavaScript and the onclick (or onkeypress) event.
The javascript:
<script language="JavaScript" type="text/javascript"> function targetBlank (url) { blankWin = window.open(url,'_blank','menubar=yes,toolbar=yes,location=yes,directories=yes,fullscreen=no,titlebar=yes,hotkeys=yes,status=yes,scrollbars=yes,resizable=yes'); } </script>
The anchor:
<a href="http://mindspill.net" onclick="targetBlank(this.href);return false;">mindspill.net</a>
It will generate this link: mindspill.net.
Also See
If you want a truly accessible link, which does not rely on Javascript, read this article: A List Apart: Articles: Accessible Pop-up Links.