Literally Google Webmaster Guidelines say:
"Use robots.txt to prevent crawling of search results pages or other auto-generated pages that don't add much value for users coming from search engines."
So a couple of questions:
- What is of value for a user?
- Who is determining the value for the users in these cases?
As always, it's not always quite clear on what treatment you should use for search pages!
So a couple of questions: - What is of value for a user? - Who is determining the value for the users in these cases?
As always, it's not always quite clear on what treatment you should use for search pages!