What could cause for a page to get not indexed?

[Naksh]

The Top Reasons Why Google Isn’t Indexing Your Site
1. Your Site is Indexed Under a www- or Non-www Domain
2. Google Hasn’t Found Your Site Yet
3. The Site or Page(s) are Blocked With robots.txt
4. You Don’t Have a sitemap.xml
5. You Have Crawl Errors
6. You Have Lots of Duplicate Content
7. You’ve Turned On Your Privacy Settings
8. The Site is Blocked by .htaccess
9. The Site Has NOINDEX in the Meta Tag
10. You Have AJAX/JavaScript Issues
11. Your Site Takes Forever to Load
12. You Have Hosting Down Times
13. You Got Deinedexed

[ritesh3592]

Following are some of the reason due to which your page has not index yet.
-Google Hasn't Found Your Site Yet
-The Site or Page(s) are Blocked With robots.txt
-You Don't Have a sitemap.xml
-You Have Crawl Errors
-You Have Lots of Duplicate Content

[atocloud]

The Top Reasons Why Google Isn’t Indexing Your Site
1. The Site or Page(s) are Blocked With robots.txt
2. You Don’t Have a sitemap.xml
3. You Have Crawl Errors
4. You Have Lots of Duplicate Content
6. You’ve Turned On Your Privacy Settings
7. The Site is Blocked by .htaccess
8. The Site Has NOINDEX in the Meta Tag
9. You Have AJAX/JavaScript Issues
10. Your Site Takes Forever to Load
11. You Have Hosting Down Times
12. Yous Got De-indexed by google bot