Why some of my articles of my blog have been indexed while some haven't? I am a fresh in SEO industry. Please give me suggestion. Thank you!
I doubt anyone will be able to give you the correct answer this is how search engine are. Normally each time they crawl a site the only crawl some of the links i have always seen this but over time they will crawl more and more of the pages you should submit a sitemap this can help your pages get detected faster. If you want a page found put the link to it easy to find for a spider like on the top of the homepage.