Bazaar Voice provides a pretty easy-to-use product review solution for websites (especially sites on Magento): https://www.magentocommerce.com/magento-connect/bazaarvoice-conversations-1.html If your product has over a certain number of reviews/questions, the plugin cuts off the number of reviews/questions that appear on the page. To see the reviews/questions that are cut off, you have to click the plugin's next or back function. The next/back buttons' URLs have a parameter of "bvstate....." I have noticed Google is indexing this "bvstate..." URL for hundreds of sites, even with the proper rel canonical tag in place. Here is an example with Microsoft: http://webcache.googleusercontent.com/search?q=cache:zcxT7MRHHREJ:www.microsoftstore.com/store/msusa/en_US/pdp/Surface-Book/productID.325716000%3Fbvstate%3Dpg:8/ct:r+&cd=2&hl=en&ct=clnk&gl=us My website is seeing hundreds of these "bvstate" urls being indexed even though we have a proper rel canonical tag in place. It seems that Google is ignoring the canonical tag. In Webmaster Console, the main source of my duplicate titles/metas in the HTML improvements section is the "bvstate" URLs. I don't necessarily want to block "bvstate" in the robots.txt as it will prohibit Google from seeing the reviews that were cutoff. Same response for prohibiting Google from crawling "bvstate" in Paramters section of Webmaster Console. Should I just keep my fingers crossed that Google honors the rel canonical tag? Home Depot is another site that has this same issue: http://webcache.googleusercontent.com/search?q=cache:k0MBLFcu2PoJ:www.homedepot.com/p/DUROCK-Next-Gen-1-2-in-x-3-ft-x-5-ft-Cement-Board-172965/202263276%23!bvstate%3Dct:r/pg:2/st:p/id:202263276+&cd=1&hl=en&ct=clnk&gl=us