Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

HTML How to Make a Website HTML First Build Structure

What is the different between?

What is the different between <!DOCTYPE html>, <html></html> and index.html when they all represented for one purpose?!! I mean it all saying that this is an html file or codes why not only one thing not the 3, is there a specific function for each one separately?!

Navid Mirzaie Milani
Navid Mirzaie Milani
6,274 Points

<!DOCTYPE html> is an instruction of which html version you gonna use in your html document. In this case <!DOCTYPE html> is an HTML 5 doctype, which means your document will accept HTML 5 tags and wil validate your document on those rules that already set by W3C. you can use HTML 4.01 Strict, XHTML 1.0 Strict etc.

More information about doctypes

1 Answer

J.D. Sandifer
J.D. Sandifer
18,813 Points

"<!DOCTYPE html> is an instruction of which html version you gonna use in your html document. In this case <!DOCTYPE html> is an HTML 5 doctype, which means your document will accept HTML 5 tags and wil validate your document on those rules that already set by W3C." - Navid