Duplicate URL Fix
This page was written in English, please see the English version for the correct code changes.
As of PS 1.4.3, all these issues have been addressed, if your theme was created after PS 1.4.3 was released, or has all the latest changes from it, you don't need to do anything, otherwise, consider upgrading to the latest Prestashop version.
There is a big problem with extra variables on pages which list products (category, search, best seller, specials and new products).
The sort by, # or results per page + language flags create new links with a potentially endless number of variables.
While those URLs are not a problem for regular users, search engines that crawl your site find those links, then they crawl those links and find more new links on them with even more variables added at the end.
For search engines, the sort order of products on a page, the number of result per page, and a language change variable are not needed, in fact, they just add new links for them to crawl with virtually the same data.
We estimate that the extra URLs that search engines crawl are about 50-100+ times more than that actual URLs that are valid and need crawling, this results in a lot of meta tag duplication, very similar content, and creates a huge load on your site when they crawl pages that are not really needed.
The ideal solution is to hide all those extra variables from search engines, the only variable that should be available is the page number (when pagination is present).
This will make sure there are no multiple URLs for the same page with different variables.
This modification also includes the Multilingual URL Fix
This fix will prevent Search Engines from seeing these new pages, however, if they already crawled your site and have those links, they will continue to crawl them unless told otherwise.
We have added to the Duplicate URL Redirect module 301 redirects from each page with variables (11-category-name?orderby=name&orderway=asc) to the page without any variables (11-category-name).
The only variable that will stay is p= which is used for pagination.
Download the modified files from http://www.presto-changeo.com/SEO_Fix.zip (4 in total) for PS 1.2, 1.3 and 1.3.2, make sure you keep a backup of your existing files before copying the 3 modified ones.
HOW TO TEST?
This change does not affect regular users, so to test it, you need to trick the server to think you’re a search engine.
1) Open Firefox, in the address bar type “about:config” and press enter.
2) At the top there’s a filter, type “agent”
3) Right click on “general.useragent.extra.firefox” and choose modify.
4) Replace the value inside with “bot” and click OK
Now when you access your site, the module will you are a search engine, and apply the changes.
You will see that choose a filter will not do anything, the Results per page dropdown is gone, and if you enter one of those URLs with extra variables, they will all be stripped out (except p= if it was present).
To return the browser to normal, right click on “general.useragent.extra.firefox” and click on “reset”.