What is doctype used for?

Related questions

1. What is .xml used for?
2. How is HTML different from XML?
3. For what XML is used?
4. What is Whatwg URL?
5. What is XML and why do we use it?
6. What is the need of XML?
7. What is the purpose of the doctype command?
8. What is the advantage of XML?
9. How is XML related to HTML?

Tags

1. #which
2. #doctype
3. #check
4. #modes
5. #markup
6. #software
7. #against
8. #browsers
9. #rules
10. #rendering
11. #kinds
12. #things
13. #document
14. #validators
15. #should
16. #different
17. #determine
18. #later