target="_blank" means a new window distinct from any existing window. If you were to use a name instead, like:
target="bob"
and use the same name for all of the links, they will reuse the existing named window if it is already open:
HTML Code:
<a href="http://www.google.com" target="bob">Google</a><br>
<a href="http://www.yahoo.com" target="bob">Yahoo</a>
That's just straight HTML, no javascript required unless you want to control other aspects of the new window. Even with javascript, if you target the same window each time, it will be reused if open.
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