George Pattichis

Link Juice Keeper redirects all non-existing URLs, that normally return a 404 error, to the page/post of your choice. This way everyone who comes to your blog via a broken link (both people and robots) will be redirected to a valid page.
A 404 Error (Page not Found) is very common and one of the main reasons Google can give you a lower ranking. Taking steps to handle 404 errors can be complex for non-techy users. With this free plugin you can finally resolve all 404 errors with just 1 click!
<h3>What are 404 errors?</h3>
As you probably know, incoming links play important role in ranking well in Google and other search engines. Therefore you should ensure that every incoming link leads to one of your valid pages on your blog. This may be a challenge because your website is dynamic and it changes every day:
<ul>
<li>you might remove or unpublish posts or pages;</li>
<li>you might change your URL structure on your blog;</li>
<li>links may brake because of technical misconfiguration;</li>
<li>a webmaster might add your link in their posts with a typo;</li>
<li>a visitor may simply mis-type your post’s URL</li>
</ul>
Any of the above will lead to link juice waste and a 404 error. You can avoid this simply by installing this plugin.
<h3>Features</h3>
<ul>
<li>Redirect errors to your homepage, an existing page, post or even a custom link</li>
<li>Monitor/log all 404 errors (Optional)</li>
<li>Choose redirect method to be used (301,302,307)</li>
<li>Send email notifications on every 404 (optional)</li>
<li>Translations ready</li>
</ul>
Link Juice Keeper was originally developed by <a href="https://profiles.wordpress.org/sirzooro/" rel="nofollow ugc">Daniel Frużyński</a>. The plugin has been adopted and refactored by <a href="https://profiles.wordpress.org/pattihis/" rel="nofollow ugc">George Pattichis</a> who will continue development and maintenance.
<a href="https://wordpress.org/extend/plugins/link-juice-keeper/changelog/" rel="ugc">Changelog</a>

Link Juice Keeper

Improve your SEO and keep your link juice by automatically redirecting all 404 errors to any page/post/url. User friendly options and log feature.

MrXHellboy

Track your 404 hits!
Do you keep track of your 404 not found hits ? If you don’t, try this simple plugin. 
It will keep track of the hits on your 404 not found page.
Useful for what ?
Well, probably you removed or relocated some categories, pages, posts etc etc a while ago or maybe just a couple of weeks without knowing anymore. 
Right now it sucks search engines already checked your website and took a notice of those URI’s or maybe you have some anchors on your own website pointing to moved URI’s. 
Those visitors arrives on your 404 not found page with a notice that the page they are looking for not exists anymore. 
Some visitors will stay on your site and look for the particular page, but the other group leaves immediately. What a shame…
What does this plugin do ?
This plugin tracks those visits on your 404 – not found page. It stores the time, requested URI and Referer. 
More information is absolutely not needed. The time and referer does already overdo it, but maybe you can get some extra information out of it. 
Thos information is stored in a txt file since i found it quite useles to create a new table or use the database in the first place. 
With 1 single click on the button you empty the file when you’re done with taking the appropriate actions on the results. 
You may want to add rewrite conditions @ your .htaccess file or use a seperate plugin for adding redirects. 
You can check the report within the admin settings menu – 404 report
How do i get it to work ?
Simple! 
1) Upload this plugin into your plugin directory. Activate the plugin: admin->plugins. 
2) Open your 404.php page within your theme and add the following snippet somewhere on that page. 
[php]
404 reporting
if (class_exists(‘NotFound_404’)){ 
 $Error404 = new NotFound_404(); 
 $Error404->Log404Error(); 
} 
[/php] 
3) Change the permissions (CHMOD) of the file 404.txt to 600.
Have fun logging!
<h3>Development Blog</h3>
<a href="http://online-source.net/category/scripts/wordpress-plugins/" title="Online-Source WordPress plugins" rel="nofollow ugc">Online-Source WordPress plugins</a>

Link Juice Keeper vs 404 Not found report