At this point you are not able to customize your affiliate links and make them look pretty.
You can not make an affiliate links (e.g. http://www.shareasale.com/r.cfm?u=[partner-id]&b=[extra_attribute_1]&m=[program-id]&afftrack=&urllink=[deeplink-url-encoded]) look like: yourdomain.com/product
We are however working on such a feature so it will become available sometime in the future.
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