In biology, cell theory is a scientific theory which describes the properties of cells. These cells are the basic unit of structure in all organisms and also the basic unit of reproduction.
The doctype declaration should be the very first thing in an HTML document, before the <html> tag. The doctype declaration is not an HTML tag; it is an instruction to the web browser about what version of the markup language the page is written in. The doctype declaration refers to a Document Type Definition (DTD).
html files are created for the purpose of being displayed in a user s web browser allowing the formatting of text images and other website content the html code itself is not actually seen by the user instead the resulting website page is viewed in the user s web browser