This is the number of pages on your website that are indexed by search engines. It's important to aim to have all of your web pages crawled and indexed by the search engines, as this gives you more opportunity for your website to be found.
A low number (relative to the total number of pages/URLs on your website) indicates that there is an issue, whether it's due to a bad internal linking structure, or you're unknowingly preventing search engines from crawling your pages.
Make sure your website's XML sitemap is present and you have submitted it to the major search engines. Building backlinks to your website's internal pages will also help bots to discover, crawl and index them, while building authority to help them rank in the search engines.
Check Google™ Webmaster Tools under 'Google Index' and 'Crawl' to keep track of the status of your site's indexed/crawled pages.
Good, the URLs look clean.
Underscores in the URLs
Font Size Legibility
Custom 404 Page
Great, your website has a custom 404 error page.
Take advantage of the opportunity to provide a beautiful 404 Error Page for your visitors.
Structured Data Markup
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