How do I add code to the head of the html?

I use Dynamic Drive to assist in getting html code to do cool 'tricks' on my pages.
Some of those include code that must goto the head section of the code.

example would be a java to open links in a new 'custom' pop up window - planning reunion giving links to locations for the event into a pop up window instead of redirecting them away from our site.

How would we add such code like this below... it is java code

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