What are the reasons for page de-indexing of a site that has no SEO issue? - Webmaster Q and A

1. Violation of Google Policies:
If a website violates Google's guidelines, the site can be de-indexed, which means it won't show up in search results. This can happen if the site is engaged in black hat tactics such as spamming, keyword stuffing, or cloaking.

2. Manual Penalty:
Google's spam team can manually review a site and issue a penalty if they believe the site engages in practices that violate their guidelines. This can result in a site's removal from search results.

3. Duplicate Content:
If a site has duplicate content across different pages, Google may de-index the affected pages. This can happen if a site has been designed improperly, or if it's been hacked and malicious content has been added.

4. Malware or Hacking:
If a site is compromised by malware or hacking, Google may de-index the affected pages. Search engines can't risk allowing malware or viruses to spread through their search results, so they take quick action to protect their users.

5. Expired Domain:
If a site's domain registration has expired, the site will no longer be indexed by search engines. This can happen if the site owner forgets to renew their domain registration, or if they intentionally let it expire for some reason.

6. DMCA Takedown:
If a site receives a DMCA takedown notice, it may be removed from search results for infringing on copyrighted material. This can happen if the site has used images, videos, or text without permission.

7. Site Restructuring:
If a site undergoes a major restructuring, such as a URL change, and the site owner fails to properly redirect the old URLs to the new ones, search engines may de-index the old pages. This can happen if a site owner isn't familiar with best practices for SEO.

* For more understanding about the question, consult a webmaster or SEO expert.