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).
In this tutorial viewers will learn how to embed videos in a webpage using HTML5. Ensure your DOCTYPE declaration is set to HTML5: <!DOCTYPE html>: Use the <video> tag to insert a video. Define the src as the URL of your video; this is similar to â¦ html