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tedster - 7:00 pm on Oct 10, 2010 (gmt 0)
There might be some other way - but with HTML5 the target attribute is legitimate and the browser support for it is certainly fine.
If you need the page to validate, you can just change the DTD to <!DOCTYPE html> and you are future-proof, as far as I can see - unless your page depends on quirks mode, that is. The HTML5 DTD always triggers standards mode.