Question about building webpages

I have just finished all of the exercises for the “New Responsive” section where users have to build a cafe menu. I am going back through and taking notes. I wanted to ask something: for the first lesson, we are asked to input a “!DOCTYPE” and below it a HTML tag for English. My question: do we have to put the “DOCTYPE” and English tag for all webpages that we build?

doctype is needed for html code.

html tag is not in theory required but if you want google and other search engines to easily present your site in the language it is using then you should include the tag and the lang attribute. (also not including it can lead to other problems with the way the page may be presented on different browsers or how it is read by text to speech readers)