Ariana

This is a very simple plugin that adds a “robots” meta tag to the head of your site with “noindex” in it.
The effect of the noindex robots meta tag is that search engines will not index your pages and posts at all. 
This is a better solution then the wordpress default settings option, which tells search engines to not crawl the URLs in the robots.txt. Because Google (and other search engines) sometimes still index URLs they haven’t crawled, for which they determine relevancy based on anchor text of links which lead to the specific URL.

Simple Noindex

Samir Shah

Matt Calvert

This plugin issues an HTTP <code>410</code> response for URLs corresponding to content that has been permanently removed from your site. Originally created by Samir Shah, now maintained by Matt Calvert. When a post or page is deleted, the plugin logs the old URL and returns a <code>410</code> response when that URL is requested. You can also manually manage the list of obsolete URLs.
The <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.11" rel="nofollow ugc">HTTP Specification</a> defines the <code>410 Gone</code> response for resources that have been permanently removed. It informs search engines and crawlers that the content will not return, improving crawl efficiency and SEO clarity.
This plugin is actively maintained by Matt Calvert as a personal project, informed by previous professional experience with similar 410-handling logic. No proprietary or employer-owned code has been used.

HTTP 410 (Gone) responses

Sends HTTP 410 (Gone) responses for deleted content, telling search engines the page is permanently removed.

Simple Noindex vs HTTP 410 (Gone) responses