George Stephanis

Simple 404 Keyword Insertion creates a page called “404-page” on activation. When a visitor hits a 404, the plugin serves that page with a <code>[404-keywords]</code> shortcode replaced by the sanitized keywords from the request URI. This helps create SEO-friendly 404 pages that reflect the content the visitor was looking for.

Simple 404 Keyword Insertion

Builds a custom 404 page based on the request URL, inserting the keywords from the failed request into your 404-page content.

GB071

ecreateinfotech

This plugin automatically converts keywords in a post/product title and category to tags upon saving. It includes a user-editable list of words you want the plugin to ignore
<ul>
<li>Converts keywords in post/product titles to tags</li>
<li>Converts keywords in post/product category to tags</li>
<li>Includes user-editable list of words to be ignored</li>
<li>Setting to enable for title and category separately</li>
<li>Setting to overwrite previous tag and consider only title and category while generating new one</li>
<li>Converts on publish and update.</li>
</ul>
Multi-blog adminstrators take note: this plugin is especially helpful if you’re building a community-based site where tagging is important and your bloggers are not always diligent about tagging.

Auto Tag Creator

Automatically creates tags from post/product title and category, on update or publish.

Simple 404 Keyword Insertion vs Auto Tag Creator