You can think of product pay-per-click programs as online-comparison shopping engines or price-comparison engines. A product PPC program focuses specifically on products, so you bid on placement for your product advertisements.
The requirements for using a product PPC program are a little different from keyword PPC programs, however. With a product PPC, you must provide a feed — think of it as a regularly updated price list for your products — to the search engine. Then, when users search for a product, your links are given prominence, depending on the amount you have bid for placement. However, users can freely display those product listings returned by the search
engine in the order of price from lowest to highest if that is their preference. This means that your product may get good placement initially, but if it’s not the lowest-priced product in that category, it’s not guaranteed that your placement results will stay in front of potential visitors.
Some of these product PPC programs include Shopping.com, NexTag, PriceGrabber, and Shopzilla.
Although product PPC programs are popular for controlling the placement of your product listings, some services, such as Google Base, enable you to list your products in their search engines without cost. These product PPC programs still require a product feed, however, to keep product listings current.
Implementing a product feed for your products isn’t terribly difficult, although, depending on the number of products you have, it can be time-consuming. Most of the different product PPC programs have different requirements for the product attributes that must be included in the product feed. For example, the basic information included for all products is an item title, the direct link for the item, and a brief description of the item.
Some of the additional attributes that you may need to include in your product PPC listings include the following:
■ Title
■ Description
■ Link
■ Image link
■ Product type
■ UPC
■ Price
■ MPN (manufacturer’s part number)
■ ISBN
■ ID
Some product PPC programs require XML-formatted feeds; however, most will allow text-delimited Excel files (simple CSV files). This means you can create your product lists in an Excel spreadsheet and then save that spreadsheet as text delimited by selecting File  Save As and ensuring that the file type selected is text delimited.

Next : Service pay-per-click programs

When users search for a service of any type, such as travel reservations, they are likely to use search engines related specifically to that type of service. For example, a user searching for the best price for hotel reservations in Orlando, Florida, might go to TripAdvisor.com. Advertisers — in this case, hotel chains — can choose to pay for their rank in the search results using a service PPC program.

Service PPC programs are similar to product PPC programs, with the only difference being the type of product or service that is offered. Product PPC programs are more focused on e-commerce products, whereas service PPC programs are focused on businesses that have a specific service to offer.
Service PPC programs also require an RSS feed, and even some of the same attribute listings as product PPC programs. Some of the service PPC programs you might be familiar with are SideStep.com and TripAdvisor.com. In addition, many product PPC programs have expanded to include services. One such vendor is NexTag.
In addition to the three categories of PPC programs discussed in this text, there is an additional one. Pay-per-call is a type of keyword advertising in which search results include a phone number. Each time a call is connected through that phone number, the company that owns the number is charged for the advertising, just as if it were paying for a traditional pay-per-click service.