If your page is in a Strict doctype, then you can't use the target attribute. (In a Transitional doctype, target="_blank" will give you an endless succession of new windows, one for each link; target="anything" will give you one new window over and over, with the JavaScript name "anything", and it will keep re-using it.)
Instead, you have to use JavaScript to open the window. You can do this inline, with
:onclick => 'window.open(this.href, "someName");'
or you can use another attribute as a hook for unobtrusive JavaScript. I prefer the latter, and use