Simply give your target a unique value, like this:
<a href="http://stackoverflow.com" target="mynewwindow">Always opens in the same window</a>
This is the default behaviour of the target attribute. _blank
is one of an handful special keywords, with special behaviours, as described in the HTML standard.
Note that the standard doesn't talk about windows, but about browsing context. A browsing context is typically a window or a tab, but this is up the browser.
As for the special keywords:
_blank
means always use a new browsing context (e.g. tab or window)
_self
means always use the same browsing context
_parent
means use a parent context, if any
_top
means use the topmost context, if there are any parents
With iframes, things are a little bit more complex.
edit: Note also that the second time a user clicks the link, the target page will not be reloaded. If you need a refresh, you will have to use Javascript.