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A point of clarification here related to the first part of your answer. Google does not use PA and DA, those are Moz metrics. They're not looking at the Moz metrics for a site when they use their algorithms.

Thank you David. This information helps.

Hi Kaushal, Thanks for the question. There are a few ways to deal with this problem which are recommended by Google here. In summary, you can: Use parameter handling as you have done Add the nofollow attribute to problematic URLs Block problematic URLs in robots.txt There is also a thread in the Google webmaster forums which may be useful to you: https://productforums.google.com/forum/?hl=en#!category-topic/webmasters/crawling-indexing--ranking/CCORJBI-mEg Overall, it comes down to having a good site architecture and cutting down / removing / blocking URLs that you don't care about from a search perspective. I hope that helps a bit! Paddy

PixelKicks gave a good answer. In theory you shouldn't see much, if any, change in rankings, but in practice, any time you move pages, there is some risk.  I don't know if you can do a slow migration or not, but if you can, I'd suggest you do the following. Start small: Move a portion of the pages (maybe a couple hundred thousand for your big site) first, track their traffic and ranking and see if there is any impact.  I'd probably watch the pages for 3-4 weeks just to make sure.  If you see a drop, you may want to keep watching them longer to see if it comes back on its own.  This should give you an indication of what to expect for the other pages. Setup Canonical Tags First If you are able, setup the new pages (or entire new site) and then add canonical tags to all the old pages, pointing to the new pages.  This will actually start the transition process for Google and others and you may see the pages with canonical tags having been switched in Google in just a few days.  After you have seen that most or all the pages have been switched in Google, then setup the 301 redirects. You can see Rand talking about this process in the video on this page: http://moz.com/blog/cross-domain-canonical-the-new-301-whiteboard-friday How Long to Recover: You may not see any drop in rankings.  You may see a little shifting for a few days, but then everything settles back to where it was.  If you do see a drop, it's likely that it will recover after a few weeks or months (as PixelKicks indicated).  If, on the other hand, you see a drop and it doesn't self-correct after several weeks, then the recovery is a matter of having to rebuild some authority to your site.  The time that will take will depend on how much work you put in to doing that and what your competition is like. Good luck.  That's a huge site. Kurt Steinbrueck OurChurch.Com

This URL contains some advanced tricks to specifically prevent prefetching by Firefox. I've only tried to the htaccess mod_rewrite technique. However, I modified that technique to send prefetch attempts to an empty file instead of the normal 404 page (saving resources): http://www.petefreitag.com/item/312.cfm I would avoid only showing tags to Googlebot. It does look a little spammy and like cloaking but more than that, adjusting content for Google can be an involved coding process that comes with risks (accidentally showing something else to Google, etc.).

It's not something I've looked into much, but importantly, will search engines still be able to crawl all your content as easily as before? If so, there's the argument that it makes the user experience easier as they don't have to click through pages. It could make it more difficult for those who click through pages and might remember and want to go back to something on an earlier page number they remembered. Is it important that the user knows how far through the content they are? If so I wouldn't recommend infinite scrolling unless you have a message informing them e.g. "viewing 58 of 240" . If you haven't considered it you might want to keep your header and/or footer visible at all times so for one reason at least, the user has an easy way out. Make sure it doesn't significantly slow the page load speed down too.