This is not an element or tag. it can not have content in itself. It lets the browser know how the document should be interpreted, by indicating what version or standard of HTML (or other markup language) is being used. Because of this, it is written...

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This is not an element or tag. it can not have content in itself. It lets the browser know how the document should be interpreted, by indicating what version or standard of HTML (or other markup language) is being used. To understand it, we will break it into points.

All You Need to Know of <!DOCTYPE html>