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Hi Jenna, It's not so much the fact you have 404 pages that is the problem for SEO, but rather the fact your site is creating a problem for the search engines to crawl the site correctly and efficiently since they are getting caught in an endless loop. This can be a problem because the crawlers may get caught in the endless loop and just give up on your site and leave, which means the search engines may not be able to access the rest of the pages on your site and may have a negative impact on your rankings as a whole. One of the most important parts of SEO is to make your website as "friendly" to the search engines as possible so if they caught in endless loops then that is definitely not ideal. Hope that helps! Patrick