How to add affiliate ads (javascript based)

How do I add affiliate ads (javascript based). Everytime I create a post and go to the text tab and put the javascript link and go back to the visual tab, it won’t show:

<script type=”text/javascript” language=”javascript” src=”http://www.kqzyfj.com/placeholder-19848907?target=_top&mouseover=N”></script&gt;

Please help. Thanks.

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