(You may want to skip this one if you're not an Amazon Associate.)
I've noticed lately that when I browse items at Amazon, the URLs now take one of two forms:
http://amazon.com/exec/obidos/ASIN/0684868768/
http://amazon.com/exec/obidos/tg/detail/-/0684868768/
The former URL style has been around for some time, but the latter is relatively new. If you're an Amazon Associate, the proper way of linking to an individual item (per their linking guide) is to append your Associate code (mine is "0sil8") to the first URL style, like so:
http://amazon.com/exec/obidos/ASIN/0684868768/0sil8
But if you run across an item at Amazon with the second type of URL, this won't work:
http://amazon.com/exec/obidos/tg/detail/-/0684868768/0sil8
If you've linked to items using that style of URL (something I've seen on several sites), check your reports at Amazon...you'll find that you're not getting any Associates clickthroughs or credit for those purchases. Meg has linked to items in this incorrect fashion and has received no clickthoughs or credit for any of those sales. There's no documentation on the Associates site that says anything about how to properly link to an item using the second style, so the solution is to modify your links to the first URL style if you have it wrong.
I'm not sure why Amazon introduced the second URL style to their site. The strange thing is that their appearance is inconsistant. Sometimes a search result will return the first style and sometimes the second...and then the style will switch in the middle of a browsing session. I hope that Amazon is not doing this intentionally to thwart some Associates linkers and that they will add documentation to their site concerning the appropriate linking method for the second URL style.
p.s. I'm going to get mail about this, so I'd better mention it. Several Associates are using the following linking style to get around the "You may also be interested in these items..." page that Amazon throws at you when using a link of the first style:
http://amazon.com/exec/obidos/ASIN/0684868768/ref=nosim/0sil8
instead of:
http://amazon.com/exec/obidos/ASIN/0684868768/0sil8
That way, you land on the page you linked to, rather than the page of recommendations, and have a better chance of getting the full 15% commission on the item (the commission falls to 5% if the person clicks on anything other than the "Add to cart" button on the initial page).
The "ref=nosim" links apparently work correctly, although they are undocumented on the Associates site. However, it's unclear as to whether you make more money from using them. You're more likely to make that 15%, but you might make more in the aggregate from the recommended items you get using the first method. That is, the number of people looking to buy that item right away (say, 2 people counted at 15% apiece for a $15 item for a total of $4.50) might be offset by the number of people looking to browse and then buy (10 people counted at 5% apiece for a $15 item for a total of $7.50). The reports for my site at Amazon show that people who click through seem to browse and then buy rather than buy directly...I just need to get them into the store and Amazon will take care of the rest.