the sipliest way for you would be not using the href but to use onclick event on a links you need to restrict from opening - something like
<a href="javascript:#" onclick="location.href='http://www.yahoo.com';return false;">
test</a>
But again, if I really want to open something in a new window, you cannot do anything with any type of javascript.
Try it yourself, open your page, type in a browser address bar "javascript:void(window.open(location.href))" - and you got a new window. I actually do something like that when I want to play with popups that peaple often open without address bar.