We have GoMage Advanced Navigation v.4.6 installed on our magento site but we have found out that it caused 1000s of 404 errors in WMTs as the filters are actual links in the source code and when you open them (eg right click open in new tab) they are 404s. The only way to fix this it seems is to not decode (sanitize) the urls, but then that breaks PCI compliance. The developer is aware of the issue and are working on a fix, but its seems that this has been a know issue for a while (reading some of the reviews for it).
This is a huge issue for seo and really makes a nice extension unusable if you want to rank well.
You can see the issue on there test site.
my question is, can anyone recommend a similar extension that does not have the 404s issue? (or is there anyway to get around the 404 issue)
Thanks for replying to my post, and I looked at your demo site and it seems that is does not have the same issue. But since posting the original thread we came up with a fix with a server url rewrite to changes %3F to ?
Its not perfect but now magento sees every thing after the ? as Parameters and just ignores them if it does not recognise them instead of giving at 404, and that seems to address the issue for now ( google seems happy).
That's great you've found a way to fix that issue! If you still have live URLs with parameters, you can set parameters exclusions in Google Webmaster Tools.
Good tip about WMTs but googles is usually very good at deciding for it's self ( the content of the page will not change because the paramters are junk), + the pages are canonical too so it should be fine, but worth keeping an eye on.
Here is a Free layered navigation for Magento that can help you to improve your website's naviagtion by adding more search filters. Download it from here - fmeaddons(dot)com/magento/free-ajax-layered-navigation-extension.html