Here’s a simple web development tip that foolishly I didn’t do completely until today. Using Google Analytics, find all of your site’s 404 errors. Locate the internal errors by seeing which internal pages sent the error traffic, open the pages up, and search for broken links.
It is also critical that you find external links that are going to a 404 page within your site. Perhaps the content moved, was removed, or the other webmaster made an error with his link to your site. If it’s the later, perhaps you want to email or call the other webmaster and ask nicely for the link to change. I find that calling is a better way to connect, although many people seem to be reluctant to pick up the phone.
If you find that the link is to a page that was moved or removed, you should redirect the link in your website’s htaccess file to a relevant page within your site – or to the page that moved. It can be a pain to find the exact link that was used because Google only shows the referring website, however, you can do a site search on Google (ie search site:xyzreferrer.com yoursite.com) in Google, and you will probably find where your link originates. Instead of taking the chance that the other webmaster will remove his link, it’s probably better just to redirect it to a relevant page.
After doing this with one of my sites a couple days ago, error traffic is way down. This helps to reduce the bounce rate, which should help with Google rankings.