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There isn't necessarily anything wrong with your login, it looks like it's  carrying a referring parameter in the URL so that it knows where to send you next. Not the most sophisticated way to do it, but very common. Since it returns a 404 the easiest solution would be to make your login link/button "nofollow". You could add this to the html or javascript fairly easily. Or you could place a directive in your robots.txt file disallowing these urls, Something like: User-agent: * Disallow: *login should do the trick. (but test this) If this is a javascript code causing this, you might try wrapping the script in CDATA tags. This might also do the trick. Hope this helps. Best of luck with your SEO!