If you have redesigned your website recently, you might have lots of 404 errors that are going to effect on your search engine rankings
Code 404 refers to a “not found” error; a message that alerts you that your browser could connect to the server it was looking for, but its target page could not be found. For example, you will notice a 404 error whenever you click on a link that no longer points towards an active page.
Google says 404 errors are undesirable for SEO because on finding a 404 error, Google recognizes that the page is no longer available and removes it from its search index. It also drops all of the PageRank from links pointing to that page.
If there are lots of links pointing to inactive or non-existent pages on your site that indicate 404 errors, your PageRank will drop affecting your rank in Google’s search engine results. You are less likely to generate more traffic. Moreover, your entire website can suffer from 404 errors specific to certain pages.
Fixing your website’s 404 errors could be the perfect way to increase the flow of PageRank to your website and improve usability. The easiest and most effective way to fix 404 errors is to use a 301 redirect.
301 is an HTTP response code that signals to the user’s browser as well as Google’s search indexing robots that your content has moved permanently from one URL to another one. Unlike 404 errors, 301 redirects keep PageRank flowing to your site.
When you come across a link that delivers a 404 error, you must use a 301 redirect to redirect users to the most relevant page on your website.
For 301 redirect, if you use an Apache web server, you will need to modify your .htaccess file.