Yesterday, I got message from Google that " Increase in server errors" and " Increase in not found errors" for my website in Webmaster Tools.
This is happens because, we migrated our website into new version from asp to aspx . So, our entire URL structure was changed and our back links also goes to 404 page. And, my 50% of traffic is also gone due to this new URL structure. So, I did 301 redirection for all old URL's(400 pages) to my new page like http://www.mywebsite.com/mypage.aspx to solve current issue of " Increase in not found errors" ..
But I would like to get my old SERP and PR's for my new pages to retrieve the same traffic..
So, please anyone let me know, if any valuable suggestions to retrieve my old traffic, PR and old rankings...