The Dynamic404 component determines which page is the closest match by looking at Menu-Items and articles to find a matching alias. Alternatively, you can configure redirects yourself from within the Joomla! Administrator. This way you can even fix URL-typos made by your visitors. Also, the Dynamic404 component can be extended with Joomla! plugins that allow you to search for matches within the logic of other third party extensions.
When good matches are found, you can determine yourself what to do: You can display an optimized 404-error page to your visitors which shows a listing of all the matches, plus links to your site search. Or you can transform the 404-error into a 301 or 307 redirect to direct the visitor to the right page.
Despite what some SEO-experts have claimed, Dynamic404 will give you a higher ranking when the automatic redirection of Dynamic404 is enabled: In case of a 404-error, that 404-status never reaches the visitor, but it is transformed into a valid redirect. This makes Dynamic404 vital when migrating between major Joomla! versions (Joomla! 1.5 to Joomla! 3 for example), or when migrating com_content to your favorite CCK.
Dynamic404 helped our team with:
--Setting an article (from menu item) as the 404 page. That is such a nice feature, as now the site nav is in place, with our custom title.
--We can set the redirects to auto- this lets our client move articles from category to category as much as they want without their links breaking or needing to manually add redirects.
In addition, we had challenging issues with upgrading from Joomla 1.5 to 2.5. The support team at Yireo was extraordinary, offering assistance above and beyond.
I highly recommend the Yireo team for clear, easy to use extensions and fantastic customer service!
As author, I feel to provide some feedback anyway. You claim that Dynamic404 shows a 404-error anyway - yes, it does if it is unable to find a proper alternative in the database. It doesn't change any functionality of 404-errors here, nor does it downgrade Google ratings. What it tries to do however, is to search the Joomla! database for alternatives and if it does find an alternative, it removes the 404 and sends 301 redirect to the right page instead. It seems you have somehow not configure Dynamic404 to redirect properly yet. Unfortunate that this leads to a bad review, while a simple support request could have fixed your problem.
As far as the refund for it goes, you will need to provide access to your Joomla backend to the developers so they can try to fix this / install the extension for you and determine wheter you're eligible for a refund or not. I didn't want to do this, but I probably would have gotten a refund if I had given them access (obviously I can't be sure about this).
All in all, 2/5 because eventhough I can understand their point of view, I'm still very dissatisfied with the way things ended up.
Sorry this did not work out. There were various sides to this support-issue that made us believe that Dynamic404 was not causing the problems. First of all, Dynamic404 simply is not active when you reach a normal page, it only reacts on 404-errors. So if a normal page was working before, and suddenly it no longer was, most likely something else changed. Removing Dynamic404 makes sure that no Dynamic404 functionality is present anymore. This supports our belief that this problem was actually related to something else - perhaps enabling "mod_rewrite" in the Global Configuration while not having read the instructions on the htaccess-file?
Not now I've downloaded the Dynamic404 - simply created a menu item to make the whole "page not found" experience even more user friendly for future visitors to our - soon to be revealed - brand new compact site!
Absolutely brilliantly simple and worth the (tiny) investment