The purpose of robots header tags is that you are given control of how each page should be indexed by search engines (google, bing, yahoo, etc). The tutorial below is the correct robots header tags setting for blogspot users:
How to Custom Robots Header Tags Guide For Blogger Beginners
1. Dashboard, click Settings —> Search preferences —> Crawler dan indexing —> Custom robots header tags than click Edit.
2. You must activate the feature by pressing the "YES" Button. See picture below for more details.
3. Check the box as shown below:
The settings above are recommended so that SE indexes the blog, content, homepage, articles and does not index the archive/label, does not allow the Open Directory Project (noodp) User-agent to explore your blog.
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Of course, you can change this feature to an advanced level. But before anything is changed, it's good to know all the tags above.
Allow SE indexes all pages and web content.
Does not allow SE to index pages in search results, nor to display "cached" links in the SERP.
This tag does not allow SE to follow links on a page.
Has the same value as noindex, nofollow.
not allow SE to display a "Cached" link in the SERP.
SE is not permitted to show a brief description of the SERP of a page.
The tag does not allow SE to use metadata from the Open Directory Project on the title of a page.
SE cannot display translate a page into the SERP
The image on the article page is not allowed to be indexed by search engines.
A page will not be displayed on the SERP on certain days or hours.
As blogger writes: use this tool careful. So don't just check the box, cause your blog can get a penalty or even disappear from the search engine. If you want to blog more SEO friendly, just use the default settings as shown above.