The Destination URL option allows you to point your banner to any specific page in the merchant's site, for instance you want to promote a certain dress, you can have the banner link to the page of the dress directly, instead of going to the homepage.
Example:
http://www.affbot3.com/link-608614-7...4815?plan=324&url=http%3A//affiliatebot.com
Notice the last part of the link - "url="http://affiliatebot.com" That's the destination url.
The SubID option allows you to keep track of where your traffic is coming from, particularly if you're promoting the same program on various sites.
Example:
http:
www.abot1.com/link-2133123123?plan=123&subid=friendster,
or
www.abot1.com/link-2133123123?plan=123&subid=facebook
In this example I'm promoting the same program on friendster and facebook, so by adding the sub id, I will know how much traffic is coming from these sites individually.
I hope this helps

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