Optimising your website is one of the most important activities. If you don't, nobody can find you on Google and you can lose up to 80% of your traffic. One of the most forgotten elements of SEO is sorting out web crawl errors. These are URLs search engines have tried to access but nothing exists at the address. Look at your web crawl errors and any that exist, redirect to another page – not a 401.
This is one of those things that is simple if you know what you are doing. Give us a call if you need any help.