Basically instead of showing the error page (which to the ses looks like X duplicate pages) you are redirecting from X pages to one correct page. This should take the old gadgets out of the index (again, do not 301 0r 410 if the gadget is coming back) but keep your site reliable for visitors and search engines alike. Users want to know that your site is up to date and has few errors - that will help keep them coming back or keep them from leaving. Search engines want the same thing - if they see too many errors they may reduce how frequently they crawl your site.

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The best way to learn anything, is to question everything.