This would be continuation of my previous post about identifying, remove your indexed page from supplemental index and prevent it from indexed by search engine in future. This should become your primary concern if you see drop in visitors coming in and as well as pages loading. You will be able to trace all this thing using Google Analytic or StatCounter that I have discussed before

Google
If you read my previous post, using SEO tool from Aaron will enable you to see how much your pages are fall under supplemental index. To remove the URL manually, you must read this official blog from Google about it.

http://googlewebmastercentral.blogspot.com/2007/04/requesting-removal-of-content-from-our.html

Yahoo
Yahoo does provide tool in removing your page indexed by their bot. Thanks to SearchEngineLand where I first found this information. However this tool only allow you to remove indexed page one by one via Yahoo SiteExplorer

http://help.yahoo.com/help/us/ysearch/siteexplorer/siteexplorer-46.html

MSN Live
I don’t seem to find any tool to remove your indexed page except using robots.txt and meta tag. This is not suitable if your indexed URL is generated dynamically.

Among the main 3 search engines above, I found that Google has provided the most compelling tool in tackling this issue. One thing that I missed is, if they can remove 404 error page automatically, it would be rather helps. On Yahoo, event though the tool provided is not as efficient as Google, it still allow you removing indexed URL one by one. I’m not worried too much on MSN event though they don’t have tool for this since my URL indexed by them is less than what I have in Yahoo or Google