E-Commerce Site Crawling Problem

[13375auc3]

Our website displays all of the products in our website If you attempt to visit a category or page that doesn't exist but conforms to our site url structure. Somehow google crawled these pages and indexed them, and they have TONS of duplicate content that hurt us. How do I deal with this problem?

[EGOL]

Can you block them from indexing with robots.txt.....

.... or redirect them with .htaccess.?

[AdoptionHelp]

Two ways:

1. Find out where Google followed a link to the non-existent category pages, and get those links removed and the category pages redirected or blocked as EGOL mentioned.

2. Change your code so that non-existent categories show a 404 page, preferably a 404 crafted to gently push your user to something they may be interested in.