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).
The HTML Example Element () renders text between the start and end tags without interpreting the HTML in between and using a monospaced font. The HTML2 specification recommended that it should be rendered wide enough to allow 80 characters per line.asic elements are the backbone of any HTML document. You'll see these elements in the source code for all web pages after the doctype declaration on the first line of the page. The doctype specifies which version of (X)HTML that page is using.