For those confused about it, amazon's affiliate tags take three forms:
tag=MYID-20 (note that really old affiliates don't have the "-20" portion and countries other than the US have other numbers
and really long confusing links that have SUBSCRIBER ID in them (I can't remember if it is all one word or has _ or - between the two parts).
The tags can have a ? or & immediately before the start (which depends on the rest of the link and where in it the tag occurs).
Nothing else is an affiliate tag, just the junk Amazon uses to keep track of queries and referral pages from within the site itself.
Also note, there are some publishers now putting cloaked/shortened links in their description, telling you to cut/paste those into your browser to find other titles on sale or free and these shortened links have affiliate tags (otherwise, they could use a non-shortened link and send you to a list on Amazon). Eventually, these guys will get caught and kicked out of the affiliate program at Amazon, but in the meantime, just be aware (for those that care) that you are "clicking" an affiliate link when you follow those directions.