I have K2 blog and some articles have tags. When people click on tag e.g. "summer" they get all articles related to "summer" but that creates duplicated content.
How can I set all K2 tag pages to have no index, no follow robots rules?
You may have to insert a meta tag manually for each page into a block of content that you do not want robots to index.
<meta name="robots" content="noindex, nofollow">
You can go into your robots.txt file and disallow by url/path