Have heard some great things about using canonical tags. Can anyone with some experience using them shed some light on how and when to use canonical? I hear they are great for e commerce stores is why I ask because that is what I do. My take is that you create canonical tags to tell google that two similar pages are in fact different when without use of them, google will see them as the same and give you less credit and will not index both pages. E commerce runs the risk of this since you have many many pages and they often tend to be very similar.