There is no HTML code for that. This javascript may be put in the head of the page:
<script type="text/javascript">
onload=self.blur();
</script>
But, since it is javascript, only javascript enabled browsers will use it. And since the browser can usually only blur() a window in relationship to (an)other open window(s) in that browser session, it is best if the page that this script is on is opened using the target="_blank" attribute or the javascript window.open() method from the calling page. Example1:
<a href="minimized.htm" target="_blank">Link Text</a>
Example2:
<a href="minimized.htm" onclick="window.open(this.href);return false;">Link Text</a>
Some browsers, like Opera for example, that treat new windows as new tabs may react oddly to this strategy, as may a browser (like FF) that allows the user to choose 'open link in a new tab' by right clicking on a link and selecting that option, if chosen.
Added:
I just tried this out, and the tabbed browsers handled it well, they open the new tab and shift focus to the calling tab.