Cornerstone content or articles are a way of representing the most powerful and well written articles on your website.
If you are proud of any articles and think that article can represent your website then it is your cornerstone article.
If you are using WordPress and for SEO you are using Yoast SEO then you will find a small checkbox asking –
Is this your cornerstone article ?
As per the automated suggestions provided by yoast the minimum words per article should be 900 if you want it as your cornerstone article.
The focused keyword in your cornerstone post or article should not be used with any other post.
You must include the focused keyword in your Page Title and Meta Description.
You can take help of this pyramidal shape to understand the concept of Corner Stone article.
In this shape home page is the entry point of our website. Entry page is the most important page.
After homepage you can see two pages in the next level. These two pages are Cornerstone Content of your website.
This feature was introduced in WordPress 4.6 Update.
This image tells us that the corner stone or most important articles of our website should be visible or clickable on the home page.
Navigation should be clear and easy.
If you have articles belonging to various categories like we have on our website, you can assign cornerstone articles for respective categories.
Read Our 101 Digital Marketing Articles
Read more about this topic on official website of Yoast