There's a lot of debate about opening links in new windows, same windows. There are some sites which have uses for it. For example if you're a search engine or directory, you might want to offer opening in a new window so they don't have to click the back button if the search didn't yield what the user was looking for. While browsers might want the ability to override what the webmaster suggested, it is nice for the webmaster to be able to offer that functionality.
By the same token, a link opening in a background window could have its uses too. There is potential for abuse too. Personally, I think the browser should offer a visual cue as to what the link will do and offer an easy override. For example, when a site has a link opening in a new window, it could show up w/ a subtle highlight in the underline so you know...
I'm wondering if XHTML covers any of these things?
Actually, since the 'target' attribute is deprecated in XHTML-Strict there's no way to open a link in a new window without additional scripting. All XHTML-Strict links open in the same window. But there's no visual cue whatsoever. Could be done with a title="" attribute.